Additive Synthesis
The process of constructing a complex sound using a series of fundamental frequencies (pure tones or sine waves). Each of the fundamental frequencies usually has its own amplitude envelope which allows independent control of each partial (harmonic). Pipe organs or Hammond organs are both instruments which are based on additive synthesis. Some modern synthesizers have employed additive synthesis techniques, but other techniques such as FM (see WFTD archive FM Synthesis) and physical modeling (see WFTD archive Physical Modeling Synthesis) have proven to be easier to develop and still very effective at producing a wide variety of sounds.

AM
Abbreviation for Amplitude Modulation. AM is most known as a type of radio transmission scheme. It works by taking a carrier wave of some steady frequency (the frequency of the radio station) and modulating its amplitude based upon the audio signal to be transmitted. So if you were to transmit a 1 kHz sine wave over AM, you would vary the amplitude of the AM carrier wave 1000 times per second by an amount that represents the amplitude of the 1 kHz wave. When the AM signal is picked up by a receiver the carrier wave is stripped away leaving the original audio signal, which can then be amplified.Amplitude Modulation is also a synthesis technique. While not as popular as its FM and subtractive synthesis counterparts, it has been an integral part of a few very well respected synthesizers over the years.

Architecture
A term loosely used in music technology to point to the structure of components (hardware or virtual) making up a device or process. A device's architecture is its makeup in terms of inputs, outputs, and the kinds of processes it does in what order. The architecture of a synthesizer, for example, would include its sound source (oscillators perhaps), filtering, and envelope generator, plus any effects processors or other real time controllers. It would also include the outputs and in general can include everything about the instrument's functionality. These days there are many instruments and processors that have such powerful software they can actually redefine themselves with different architectures. Kurzweil's popular VAST (Variable Architecture Synthesis Technology) is an example of such flexibility. While VAST doesn't totally reconfigure the entire instrument it does allow for a variety of radically different synthesis techniques to be employed in the one hardware platform. There are numerous other examples.

Carrier
In radio systems the carrier is the transmitted electromagnetic wave that is modulated by some means to carry information. In AM radio the carrier wave is at a fixed frequency, but its amplitude changes according to the signal contained within. In FM the center frequency is known, but the signal's frequency changes around this center point according to the information carried. More amplitude creates a wider deviation from the center frequency. There are other types of modulation that may change phase or other attributes. When a carrier wave is "demodulated" by a radio receiver the information contained within is pulled out (by removal of the carrier wave) and subsequently amplified. The frequency you tune your radio or television to in order to pick up a station corresponds to the carrier frequency.FM synthesizers also use this paradigm to generate sound. In that case the carrier is usually the sound you hear, but it is modulated by other operators to change its timbre and other characteristics to achieve the desired sound.

CoreMIDI
CoreMIDI refers to the built in MIDI support available in Mac OS X. It allows for you to set up what devices are attached to any interfaces with Mac OS X drivers. You can assign device names and attributes such as which channels they can work with, and what other features they may support such as MIDI Clock and/or Machine control. CoreMIDI is basically a built in system that gives you the power and flexibility in your MIDI system as OMS and/or FreeMIDI does under OS 9. Another advantage is that currently any CoreMIDI enabled application under OS X can utilize MIDI Time Stamping (MTS) with any of the MOTU MIDI interfaces.

DCO
Abbreviation for Digitally Controlled Oscillator. A DCO serves the same purpose as a VCO in synthesizers, only it is under digital control instead of being controlled by an analog voltage. DCO's tend to be much more stable and less susceptible to environmental conditions - especially with regard to tuning - than their analog counterparts, but some synthesists complain they are too sterile and perfect sounding.

Digital Synthesizer
A synthesizer that uses digital signal processing (DSP) techniques to make sounds. The very earliest digital synthesis experiments were made with general-purpose computers, as part of academic research into sound generation. Perhaps the best way to begin to understand digital synthesis is to compare it to analog synthesizers. Modular analog synthesis uses voltage to perform its three primary functions. A voltage-controlled oscillator (VCO) produces a tone, which is shaped by a voltage-controlled filter (VCF). The amplitude of the resulting sound is processed by a voltage-controlled amplifier (VCA). (These basic building blocks can be rearranged in a variety of ways, but they still perform similar duties.) Digital synthesis replaces voltage with numeric representations of values; so at its most basic, a digital synthesizer uses a digitally controlled oscillator (DCO), filter (DCF) and amplifier (DCA). However, the broader range of processing power available with DSP has allowed many variations of synthesis techniques to emerge that simply weren't possible with analog technologies. Early commercial digital synthesizers used simple hard-wired digital circuitry to implement techniques such as additive synthesis and FM synthesis. Other techniques, such as wavetable synthesis, physicalmodelingsynthesis and granular, became possible with the advent of high-speed microprocessor and digital signal processing technology. Some digital synthesizers now exist in the form of "soft synth" software that utilizes conventional computer hardware for processing. Virtual analog synthesizers, whether in hardware or software form, are in fact digital synthesizers that emulate the behavior of analog circuitry.

DLS
Abbreviation for DownLoadable Sounds. The DLS Specification, which was adopted by the MMA in 1999, defined the first industry-standard approach to delivering sound sets for sample-based ("wavetable") synthesizers. DLS allows composers and sound designers of CD-ROM and Internet-based content to develop custom sound sets and achieve consistent playback across a broad number of existing and pending devices. A DLS-compatible synthesizer becomes an expressive and interactive audio reproduction engine that performs as the composer intended. The combination of MIDI messages controlling small sound samples, as opposed to the use of streaming digitized audio, makes DLS handy for interactive multimedia applications, and for putting sound and music on web pages where fast downloading, seamless playback, and user interaction are critical. The level 1 specification describes a minimal synthesis architecture and feature set needed for a device to be capable of playing DLS-format sound samples. Later levels (DLS-2, etc.) address enhanced performance and features, and may include different methods of synthesis.

Envelope
In sound and synthesis, the envelope is the variation that a sound exhibits over time - basically how a sound starts, continues and disappears. It is comprised of concepts such as attack and decay, but other sonic distinctions such as transient and sustain may also be applied in some circumstances. Pitch, timbre, and harmonic content (which is basically timbre) can also change over time and in some cases are considered part of the overall envelope making up a sound.

FM Synthesis
The generation of complex signal waveforms in electronic music by Frequency Modulation of one or more sine wave signals by other sine waves (or other waveforms). FM synthesis as a method of generating complex musical waveforms was pioneered by John Chowning at Stanford University, and has shown that an extremely wide variety of waveforms may be made this way. The method also requires significantly less hardware than other similar methods, such as additive synthesis. One of the first commercial synthesizers to use FM synthesis was the Synclavier, produced by the now defunct New England Digital Corp. Easily the most famous FM synthesizer, however, is the Yamaha DX-7. This keyboard brought FM synthesis to the masses and is still renowned for its pure bell like tones and electric piano sounds.

FreeMIDI
FreeMIDI is a complete MIDI operating system for the Macintosh and handles all MIDI communication between various pieces of hardware, including the Mac CPU and MIDI interfaces, and any Free MIDI compatible MIDI software. It ships free of charge and is automatically installed with all Mark of the Unicorn music software products. It comes in the form of a FreeMIDI system extension, an optional OMS emulator extension (to emulate the Opcode MIDI System), and a FreeMIDI Folder, which resides in the top level of the System Folder. FreeMIDI automatically detects what type of MIDI interface is connected to the Macintosh modem and/or printer port, automatically detects what MIDI devices are connected to interface (it "knows" over 200 types of devices), and provides the user with a graphical representation of their MIDI studio. It also provides pop-up sound lists for over 100 popular MIDI synthesizers-as, generic support for any General MIDI device, and advanced features such as inter-application communication, and multiple application real-time synchronization.

Freeze
A function of some DAWs that enables a particular track (or group of tracks in some cases) to be rendered. In fact, in most ways freeze (which does go by other names in some software) is just another term for render, but applies to the unique characteristics of an audio production system. The idea is to be able to reduce the strain on the host computer by changing real-time processes in audio files written to disk. For example, let's say you have a soft synth track being processed by a series of plug-ins. You could freeze the track, which would basically record the whole setup, including the results of the various plug-ins to disk. Now each time you play the part back, your computer is able to easily read a single audio file from disk rather than having to do all the synthesis and processing in real-time. If you change some parameter or make an edit, the track becomes "un-frozen" or unrendered again so it's back to being a live track - and you must freeze it again to rewrite an updated audio file.

Frequency Modulation (FM)
The changing of the frequency of a "carrier" in response to a "modulating" signal, usually an audio waveform. As the modulating signal voltage (amplitude) varies up and down the frequency of the carrier varies up and down from its nominal unmodulated value. In music, vibrato is a form of frequency modulation because it is a periodic variation in frequency (pitch). In FM broadcasting the audio signal is used to modulate a high frequency carrier that is then transmitted. At the receiving end a special circuit called a FM detector, or "discriminator" is used to recover the audio from the modulated signal. FM is considered a better (than AM - Amplitude Modulation) method of transmitting radio and TV signals because the FM signal is not as sensitive to amplitude variations caused by atmospheric interference. FM is also used as a sound synthesis technique (see FM Synthesis).

FUN
Abbreviation for "Function." A component of the V.A.S.T. synthesis architecture found on Kurzweil K-Series synthesizers, beginning with the K2000 in 1991. FUNs are a series of equations you can use to modulate control-source signals, from physical MIDI controls like the Mod Wheel to software control sources such as LFOs and attack velocity. FUNs take these control sources one level further. By setting up a FUN as a control source, you can mix the signals of two control sources, and perform one of many functions on the combined signals. The result of that function becomes a new control source value. Because they can radically change their combined input values, FUNs can have a profound effect on sounds. FUNs combine two different control source inputs, such as an LFO, a MIDI controller, a numerical value, or even another FUN. For example, the FUN equation sin (a+b), where a is an LFO and b a numeric value, can transform a sawtooth wave into a smooth sine wave or an extremely complex waveform, depending on the input value. You can access FUNs by entering the Program Editor, then using the soft buttons to select the FUN page. The best way to understand the use of the FUNs is to set up a simple test model (say, a single-layer program built on a dull sawtooth wave), then plug in the different equations and listen to their effects. The more you play around with FUNs, the better you'll understand how powerful they are.

General MIDI Lite
A variation of the General MIDI specification that has been approved and adopted by the MIDI Manufacturers Association to accommodate a new generation of new tone generators found in mobile telephones and other handheld devices. The General MIDI Lite device specification is intended for equipment that does not have the capability to support the full feature set defined in General MIDI 1.0, with the understanding that reduced performance parameters may be necessary in some mobile applications. The most apparent feature of GM Lite is its limit of 16-note polyphony, compared to GM 1’s 24-note maximum and GM 2’s 32-note specification. In addition, GM Lite recognizes a reduced set of 7 control change messages plus pitch bend (in contrast to GM 2’s 20-plus controllers). GM Lite supports the GM 1 instrument and percussion sound sets. A list of the significant specifications for GM Lite appears below. GM Lite is one of two recent variations of the MIDI specification for mobile devices. The second, SP-MIDI, is designed to address the varying polyphony capabilities encountered in different cell phones and handheld devices. General MIDI Lite Specification 16 simultaneous notes 16 MIDI Channels - Simultaneous Melodic Instruments = up to 15 - Simultaneous Percussion Kits = 1 (Channel 10) SUPPORTED CONTROL CHANGE MESSAGES - Modulation Depth (cc#1) - Channel Volume (cc#7) - Pan (cc#10) - Expression (cc#11) - Data Entry (cc#6/38) - Hold1 (Pedal) (cc#64) - Pitch Bend - All Sound Off, All Notes Off, Reset All Controllers

Granular Synthesis
A sophisticated (and esoteric) form of additive synthesis (see WFTD archive Additive Synthesis) combining sound elements called "grains," which are used to make up sonic "events." Events are time sliced into "screens" that end up containing the amplitude and frequency dimensions of hundreds of events. Very complex sounds can be created using this technique, but the computational power required to generate them is so great that it has not been practical to use this form of synthesis in any commercially available hardware machines.

Inter-Application MIDI
Many modern MIDI based software applications have the ability to communicate MIDI data with each other inside the computer. Generally this takes the form of some type of synchronization information such as MIDI clock, MTC, or actual MIDI performance data. The idea is to allow two programs that may or may not be independent applications to directly communicate necessary MIDI data with each other without having to route that data out of the computer's MIDI interface and then right back in on another port. Inter-Application MIDI has sort of taken over where the IAC left off a few years ago, but it is essentially the same technology.

Inverter
An inverter is an electronic device that changes a DC voltage to a pseudo AC voltage. "Pseudo" because the wave is not smooth like a true AC sine wave. By pulsing the DC voltage off and on at time sensitive rates and varying voltage levels an AC sine wave is approximated. There are many approaches to this process that may sound familiar to synthesists, such as frequency modulation, pulse width modulation, etc. Generally here is how it works: A true 120v sine wave is like a circle stretched out over time moving above and below a reference (usually zero volts). Normally, it starts at zero volts, rises to its peak at about +165v, goes back to zero then down to -165v and then back to zero in 160th of a second. (In the U.S. our voltage operates at 60 Hz or at 60 sine waves per second.) An inverter approximates this action by pulsing the DC voltage on and off for short bursts of time slowly increasing the voltage from zero up to +165v and then back down to zero and then down to -165v and then back up to zero. A very simple inverter might turn the voltage on at 40 volts and then turn it off, on at 80 volts, off, on at 120 volts, off, on at 165 volts, off, on at 120 volts, off, on at 80 volts, off, on at 40 volts, off, wait, on at -40volts, off, on at -80v, off, etc. until the sine is completed. This does not produce a real sine wave, but to some electrical loads it is close enough. Capacitors can be used to smooth out this stepped sine wave quite a bit. These may be found in the output of the inverting device and are almost certainly found in the power supply of the device being powered unless it is a simple appliance.

Keyboard Scaling
Keyboard scaling is a parameter found in many modern keyboards. Its function is to provide a way for a sound to be altered smoothly across the range of the keyboard. This is accomplished by using the key number as a modulation source and routing it to some parameter the user wishes to alter. Level scaling changes the loudness of the sound, while filter scaling changes its brightness. In some synthesizers key scaling can be routed to many parameters simultaneously with different strengths and polarities. The practical application comes out of programmers trying to make acoustic type sounds more realistic across the entire range of the keyboard.

Linear Arithmetic Synthesis
A digital synthesis method developed by Roland in the 1980s that creates sounds by attaching the attack portion of a sampled waveform to one or more internally generated waveforms. The wildly popular Roland D-50 synthesizer utilized this type of synthesis. Human sound recognition is heavily influenced by hearing the attack of a sound. After the attack, most musical instrument sounds transform into simple waveforms. By digitally attaching a PCM sample of (for example) a trumpet attack to a digitally generated sine wave, L/A synthesis was capable of producing many realistic instrument emulations while requiring a minimum of storage space. In addition, L/A allowed sound designers to graft different attack samples to different waveforms. A classic example was the Roland D-50 patch "Fantasia", which features a percussive, bell-like attack to a sustained pad sound. Roland called these PCM samples and generated waveforms "Partials", not refer to be confused with the term used in the sense of harmonics. Each Partial can behave like an individual synthesizer, with its own pitch and time variant amplifier plus, in the case of synthesizer waveforms, cutoff frequency, resonance and time variant filter. Two Partials grouped together created a Tone. Each Tone could utilize up to three LFOs, a pitch ">envelope, a programmable chorus and programmable EQ.

LSB
Abbreviation for Least Significant Bit. The least significant bit of any digital word is the one that, when changed, has the least affect on the overall mathematical value of the word. When looking at a word as a binary series of one's and zero's (1001001) it is the right most digit, or bit.LSB also stands for Lower Side Band, which is a term denoting the sideband produced by the difference frequencies when one signal is modulated by another as in FM synthesis or broadcast transmissions.The result of one signal or waveform being modulated by another (or others). When a signal is either frequency modulated (FM) or amplitude modulated (AM) by another signal sum and difference frequencies are produced that appear with the signal. These are known as sidebands. The Upper Sidebands (USB), which are the result of adding the signals together, and Lower Sidebands (LSB), which are the result of subtracting them. Sidebands are a phenomenon that occur in FM and AM radio stations, but they are most relevant to us because they are a phenomenon that occurs in FM Synthesis. They are a big part of what gives FM synthesizers their unique sound.

MIDI
Today's word may seem a bit basic to many of you, but we did have a request for it: MIDI - An acronym for Musical Instrument Digital Interface. MIDI was developed back in the early 1980's as a standardized protocol for communication between electronic musical instruments and peripherals. It allows MIDI devices to transmit and receive almost every aspect of a musical performance. Today MIDI is used in all sorts of applications, including synchronization, sequencing, lighting control, automation systems, more. There are many different types of MIDI messages that are used in MIDI for various applications. A typical MIDI connection is made with a MIDI cable, which has a 5-pin DIN type connector of which only three pins are used (except in some special applications).

MIDI Channel
Analogous to a television or radio channel. MIDI communication is digital, and the MIDI signals contain several types of information, often including the MIDI channel. Most MIDI messages are intended to be "picked up" by only one of perhaps many available devices that can be connected together. The channel provides an easy way to differentiate these devices. A message intended for the device on channel one, for example, will have that MIDI channel number present in its data. Only devices assigned to listen on channel one will respond to any messages with this encoding. The current MIDI specification calls for 16 MIDI channels. These 16 channels provide a way to transmit and receive 16 different musical parts all on one MIDI cable creating a convenient way to play sequences back through several keyboards, or one multitimbral keyboard.

MIDI Clock
A MIDI timing reference signal used to synchronize pieces of equipment together. MIDI clock runs at a rate of 24 ppqn (pulses per quarter note). This means that the actual speed of the MIDI clock varies with the tempo of the clock generator (as contrasted with time code, which runs at a constant rate). Also note that MIDI clock does not carry any location information - the receiving device does not know what measure or beat it should be playing at any given time, just how fast it should be going.

MIDI Control Change
Also known as or associated with MIDI Controllers or Controller Data, these MIDI messages convey positional information relating to performance controls such as wheels, sliders, pedals, switches and other control oriented devices. The information can be used to control a variety of functions in other devices through MIDI such as vibrato depth, brightness, portamento, effects levels, and many other parameters.

MIDI Delay
This is one of those terms that has been bantered around in the industry over the years and has come to have several subtly different meanings. The original meaning of MIDI delay refers to the time it takes for any active MIDI circuit to handle the signal. Just passing MIDI into, and then directly out of any device (even without doing anything to it) takes some finite amount of time because of the electronics involved in managing and buffering the signal. This is MIDI delay and in most cases it is usually well under 5 ms. The delay is cumulative though. So if you pass your signal through several devices it may be significantly delayed by the time it gets to the last device. Some people also refer to the time it takes an instrument to respond to MIDI commands as MIDI delay. While true MIDI delay is one component of this, there are other factors, such as the speed of the processor in the device. Some instruments react more slowly as they are asked to do more (for example, play more notes at once), but this is technically not MIDI delay. Some musicians claim to be able to hear/feel MIDI delay and do not like performing in situations where MIDI is used. While it's pointless to dispute what a person says they can perceive, it is important to note that given the speed of sound in air the sound leaving a speaker cabinet on the one side of a 20 foot wide stage would take about 20 ms to reach the ear of a player on the other side.

MIDI Echo
Normally MIDI data arriving at the "MIDI in" port of some device is passed on to a through (thru) port of that device if one is available. This allows many devices to share a common MIDI bus. Only MIDI data created within that device is sent out of its MIDI out port. However, when MIDI Echo is enabled data arriving at the MIDI input is "echoed" back out of the MIDI output in addition to the thru port. This data may or may not be merged with other data generated by the device.

MIDI Implementation Chart
MIDI implementation refers to the specific MIDI messages and signals a piece of gear can recognize; a MIDI implementation chart is therefore a listing of the messages a particular device can transmit and recognize. This can be very useful when attempting to determine if a device can send and/or receive various types of channel or system messages. Normally found in the back of the device's manual, its MIDI implementation chart will consist of a list of available MIDI messages, whether the device incorporates those messages, and any special notes or limitations on how it deals with those messages. For example, the chart will list the MIDI channels and modes, note numbers, and continuous controllers the device can respond to. Support for aftertouch, velocity, pitch bend (often with bit resolution), and program change will be indicated. Also listed will be recognition of system exclusive, system real time (clock commands), system common (song position, song select, etc.) and aux messages (local on/off, all notes off, active sensing, and so on).

MIDI Interface
A device that allows MIDI equipment to be connected to and work with a computer. Over the years MIDI interfaces have come in many different sizes, shapes, capabilities, and price ranges. The simplest interface has just one MIDI input and one MIDI output, providing the most basic way to get a MIDI instrument connected to a computer. More modern and sophisticated designs may have many discrete inputs and outputs as well as ports for synchronization of MDM's and other technologies. Some have the ability to resolve MIDI data to word clock, LTC, or video sync, and some even have Superclock capabilities. A few have been able to provide MIDI routing and patch bay features as well as MIDI processing functions (like changing one type of continuous controller data to another), but most newer models have forgone these features since modern software is so sophisticated with these kinds of tasks. Early models had to be built specifically for each type of computer (PC, Mac, Atari, Amiga, etc.), but recently, with the emergence of standards like USB and the decline of other computing platforms, most MIDI interfaces are cross platform and work equally well on Mac or PC.

MIDI Log Jam
When too much MIDI data is present in a single MIDI cable or between a MIDI Interface and the host computer timing anomalies can occur. This phenomenon, often called "MIDI log jam", is the result of the MIDI processor having too many time sensitive events to manage into a serialized communication. Eventually the data gets dense enough that some bytes must wait in a buffer to be sent. If the wait is long enough you can notice timing problems. It is usually a good idea to "thin out" your MIDI data some by removing any extraneous continuous controller data, or any other types of information that can generate lots of data if you notice these problems.

MIDI Manager
Software developed by Apple for the Macintosh computer to allow MIDI applications to communicate with each other through virtual MIDI connections inside the computer. Basically it works like a virtual patch bay, allowing the user to manually route MIDI data and sync information between components installed in the system. Due in part to the widespread success and usefulness of OMS and FreeMIDI, development stopped on MIDI Manager in 1995. By today's standards it is relatively slow and cumbersome to use, but there is still the occasional circumstance that requires it.

MIDI Merger
A device that merges MIDI data from two or more sources. MIDI mergers are more than just electrical combiners (or "Y" cables); they must carefully keep the MIDI bytes of data in tact, which means they somewhat intelligently look at the information passing to ensure they don't disrupt the continuity. Some MIDI mergers enable the user to give priority to one port so timing critical data - such as MIDI clock data - can pass through with minimal delay.

MIDI Mode
One of several ways in which a device can respond to incoming MIDI information. There are two parts to each mode, one defining whether it is monophonic or polyphonic, and the other determining if it is multitimbral or not. Four modes are included in the MIDI spec, and two others, Multi Mode and Mono Mode (for MIDI guitar) were developed later.

1. Omni On/Poly - Device responds to MIDI data regardless of channel, and is polyphonic. (See WFTD "Polyphonic")
2. Omni On/Mono - Device responds to MIDI data regardless of channel, and is monophonic. This mode is rarely, if ever, used.
3. Omni Off/Poly - Device responds to MIDI data only on one particular channel, and is polyphonic. This is the normal mode for most keyboards that are not functioning multitimbrally.
4. Omni Off/Mono - Device responds to MIDI data only on one particular channel, and is monophonic.

MIDI Part
Similar to what we think of as a musical part. A MIDI Part can be a drum part, bass part, keyboard part, etc. In MIDI we think of all the data on a particular MIDI channel as a "part." In a multitimbral instrument several different MIDI Parts can be played simultaneously. The structure of MIDI gives us a way to subdivide musical parts into multiple MIDI parts if we want. We can have the bass drum and snare drum be two different parts played by different instruments . Or we can have a dense keyboard layer that is actually played by multiple sound modules. Each of these may be its own MIDI Part, meaning it is separate data on a separate MIDI channel.

MIDI Port
The MIDI connections of a MIDI compatible device. A 'Multiport', or MIDI Patch bay in the context of a MIDI Interface, is a device with multiple MIDI output sockets, each capable of carrying data relating to a different set of 16 MIDI channels. Multiports are the only means of exceeding the limitations imposed by 16 MIDI channels.

MIDI Thru
Short for MIDI Through. The MIDI through is a connection available on many MIDI devices. It's purpose is to pass on (or through) an exact copy of the data present at the MIDI In of the device. This is distinct from a MIDI out, which can sometimes pass on a copy of the input, but usually has other information on it generated by the device in question. MIDI Thru allows many MIDI devices to have their MIDI connections daisy chained together all being driven by a common source or controller, which makes building complex systems much easier.

Modular Synthesizer
A type of synthesizer developed in the 1950s and popularized in the 1970s in which components such as controllers, oscillators, filters, and amplifiers are designed as separate devices and interconnected by patch cords. Every module has various control and audio input and output sockets that are used for interconnecting with the others. Early modular synthesizers didn’t have MIDI capabilities, memories, or presets, and they very rarely had hard-wired internal connections; thus, all connections were from module to module via cables. The underlying principle of analog modular synthesis is voltage control, used to control VCOs or trigger an ADSR envelope. Well known modular synths were created by Moog, Buchla, Serge, and others. A number of modular synth manufacturers continue to develop and build systems today.

Modulation
Literally, modulation is change. In music technology, the term normally applies to a control signal being used to change some aspect or parameter of another signal. For example, a regularly repeating sine waveform might be added to a pitched note to produce vibrato, or a control voltage might be used to change (modulate) a filter cutoff frequency. A whole category of synthesis (and radio broadcasting), FM (frequency modulation), is based around using the frequency of one signal (the modulator) to change the frequency of another audible signal (the carrier). Likewise, AM radio works because of amplitude modulation, or using one signal's volume to modulate another signal.

Operator
A term used in FM synthesis to refer to the software equivalent of common parts of other synthesizers such as oscillator, envelope generator, envelope amplifier, etc. The operators are combined in different ways to create different algorithms for producing fundamentally different types of sounds.An operator is also the person who runs a piece of equipment, such as a tape (machine) operator or Pro Tools operator.

OSC
Abbreviation for OpenSound Control. OSC is a protocol for communication among computers, sound synthesizers, and other multimedia devices that is said to be optimized for modern networking technology. Open SoundControl is a machine and operating system neutral protocol and readily implementable on constrained, embedded systems. It was developed by the Center for New Music and Audio Technologies (CNMAT Research) at UC Berkley starting in 1996. CNMAT Research believes that OSC offers optimized integration of computers, controllers and sound synthesizers which will lead to lower costs, increased reliability, greater user convenience, and more reactive musical control. Why? The prevailing technologies to interconnect these elements are bus (motherboard or PCI), operating system interface (software synthesis), or serial LAN (Firewire, USB, Ethernet, fast Ethernet, etc.), whereas CNMAT Research believes they have designed a new protocol optimized for modern transport technologies. OSC is currently supported by Csound, Native Instruments' Reaktor and a few others. Only time will tell whether this new protocol will be accepted and embraced by other manufacturers.

Oscillator
An electronic device which generates a periodic signal of a particular frequency, usually a sine wave, but other waveforms (square, sawtooth, triangle) are often used. Oscillators are common in audio devices such as synthesizers and test signal generators. Early synthesizers used oscillators as the basic component for all of the sounds of the machine. All of the filters and envelopes modified the sound created by the oscillator to produce the desired sound. Nowadays most keyboards produce sounds by playing back samples recorded on chips or by more modern synthesis techniques such as Physical Modeling (see WFTD archive Physical Modeling Synthesis), FM, LA, or any number of other methods that have been employed in the past 10 years.

Oscillator Sync
A phrase used in synthesis to specify a condition where a second oscillator is forced to synchronize its phase with another. This produces the sound that is characteristic of many lead synth patches or pad sounds that are very animated and change over time.

Patch
In the world of music, and specifically synthesizers, a patch is historically known as a configuration of equipment created by interconnecting them with "patch cords" (and possibly also patch bays). The action of making these connections is known as "patching." Back in the old modular synthesis days, sounds were created through the patching together of various components or modules of a synth and then refined through adjustments made to the controls of each section. In modern synthesizers the different configurations and algorithms are generally stored as a set of parameters in memory, but are sometimes still referred to as patches just the same.In the software world a patch is a quick modification of a program, which is sometimes a temporary fix until a particular problem can be solved more thoroughly.

Physical Modeling Synthesis
A type of sound synthesis performed by computer models of instruments. These models are sets of complex equations that describe the physical properties of an instrument (such as the shape of the bell and the density of the material) and the way a musician interacts with it (blow, pluck, or hit, for example).

Rompler
A slang term given to sound modules that feature stock presets based on samples stored in ROM, but generally lack in-depth synthesis technology and sampling capabilities. The term is a conjunction of the terms ROM and Sampler. In the early 1990s, Romplers became quite popular due to the proliferation of the E-MU Proteus series sound modules and other efforts by competing manufacturers. Lending quick access to relatively high-quality sounds and voices meant that composers and song-writers did not have to be synth programmers or sampling wizards as well as musicians to achieve their musical goals.

Sideband
The result of one signal or waveform being modulated by another (or others). When a signal is either frequency modulated (FM) or amplitude modulated (AM) by another signal sum and difference frequencies are produced that appear with the signal. These are known as sidebands. The Upper Sidebands (USB), which are the result of adding the signals together, and Lower Sidebands (LSB), which are the result of subtracting them. Sidebands are a phenomenon that occur in FM and AM radio stations, but they are most relevant to us because they are a phenomenon that occurs in FM Synthesis. They are a big part of what gives FM synthesizers their unique sound.

Sound font
The Sound font standard, developed by Emu Systems and their parent company, Creative Labs, is a data format that contains the detailed information necessary to create musical notes or sound effects using wavetable synthesis technology. A "Sound font bank" is a collection of sounds in the Sound font standard format. Such a bank contains both the digital audio samples captured from a sound source, and the instructions to the wavetable synthesizer on how to articulate this sound based on the musical or sonic context as expressed by MIDI. For example, a trumpet could be a particular sound in a Sound font bank that might contain both recordings of trumpets being played at several different pitches, as well as information which would tell the synthesizer to filter or mute the sounds when notes were played softly, loop information about the sample which would allow a short recording to be stretched into a sustained note, and instructions on how to apply vibrato or to bend the pitch of the note based on MIDI commands from the musician. Sound fonts get their name because the concept and their behavior is much like fonts we use in computers. Special Sound font compatible hardware is required to play Sound fonts and the quality of playback will vary somewhat depending upon the capabilities of the playback device, just like fonts we use in our computers can look different depending upon the output characteristics of our screens and printers. The main advantage to Sound fonts is they provide a tremendous amount of real time control to sound playback while still benefiting from the realism and computational simplicity of samples. As of this writing their use is mostly limited to computer sound cards (Emu does have some instruments that can use Sound fonts), but there are more ambitious hardware plans in the future.

SP-MIDI
Scalable Polyphony MIDI. SP-MIDI is a specification approved by the MIDI Manufacturers Association to handle MIDI data for "3rd Generation" mobile applications such as cellular telephones and handheld games, which have limited and variable polyphony. SP-MIDI allows composers to ensure that a song can be played comprehensibly on devices of varying polyphony by choosing the priority of MIDI channels and their available notes. It offers an alternative to the note stealing that would normally occur with a limited-polyphony device. Recently manufactured cell phones incorporate the capability to play polyphonic ringtones but different models support different degrees of polyphony - generally ranging from 4 notes on low-priced phones up to 32 notes on advanced models. SP-MIDI handles these variations with a few new concepts. First the composer defines which MIDI channels receive priority when played back by a limited-polyphony device, a process called Channel Masking. Second, the composer establishes the Maximum Instantaneous Polyphony (MIP) for each channel. SP-MIDI supports a limited number of control changes and recognizes the General MIDI 2 instrument set. Here's an example to illustrate how SP-MIDI works: A composer has written a song that contains piano, bass, drums, synth, and saxophone, with a maximum polyphony of 16 simultaneous voices. On a device capable of producing 16 voices of polyphony, all the instruments will play. If the piano and drums each use up to four simultaneous voices and the composer has given those instruments' channels the highest priority, they will both simultaneously play on an eight-voice device. If the piano channel was given the highest priority, a four-voice device will only play the piano part. While no composer relishes the thought of eliminating musical parts from an arrangement, Scalable Polyphony MIDI at least allows the writer to choose which parts play back. The MMA considers this approach to be preferable to note stealing, which the composer can't control completely. SP-MIDI compatible songs must be converted to an instruction set the cell phone or other device understands. Different manufacturers use different formats. However, several available software applications make creating these files relatively uncomplicated.

Subtractive Synthesis
One of several types of sound synthesis. In the subtractive method of sound synthesis the sound is tailored by using filters to selectively remove certain harmonics from an initial waveform. That waveform may be a complex sound, like a sample, or a simple shape created by an oscillator. Most analog synthesizers use the subtractive method.

Synthesizer
An electronic musical instrument that uses sound generating elements (such as oscillators or the like) to create audio waveforms. These waveforms are then combined with others and/or manipulated in specific ways to "synthesize" a unique sound character. Over the years many, many different types of synthesis architectures have been developed and used. Of those a relatively small number have become popular and seen widespread usage. Many modern synths provide digital control over analog parameters, such as frequency, amplitude, filtering and so on to create different timbres. Some generate these waveforms digitally.

Transwave
A specific type of wavetable synthesis used in Ensoniq instruments. It's comprised of a wavetable of sound data with a number of loops, rather than just one. These are generally called frames. Each frame has a slightly different harmonic structure, and they're arranged sequentially so that the timbres progress naturally from one end to the other. This produces a sound that will change characteristics over time as it plays through the wavetable. Additionally it is possible to have playback begin and/or end at specific points in the wavetable, and this can further be manipulated by continuous controllers.

USB
An abbreviation for Universal Serial Bus. USB is an emerging standard for interconnecting PCs with peripheral devices. The USB standard was developed by Compaq, DEC, IBM, Intel, Microsoft, NEC, and Northern Telecom to provide an intelligent serial bus for low to mid-speed peripherals. The USB standard allows new peripherals to be configured automatically upon attachment without the need to reboot or run setups. USB will also allow up to 127 devices to run simultaneously on a computer with the capability to perform isochronous data transfers, which can be assigned to meet specific bandwidth targets to support audio and/or phone and data conversations. There is not enough bandwidth, however, to do video as FireWire does. USB is a real boon to the Windows based PC community because it all but eliminates frustrating set up issues historically encountered when new peripherals must be connected. Further, as a standard it reduces the overall cost and confusion of getting devices connected to any computer.Not only is USB a new standard for interfacing computer hardware, but it also stands for Upper Side Band. This is the name given to the by-product of the new signal created when modulating a signal with another signal, as happens in broadcast and FM synthesis. The Upper Side Band is the result of summing the two signals together.

VAST
An acronym for Variable Architecture Synthesis Technology. VAST was developed by Kurzweil's Research & Development Institute prior to the release of the original K2000 (1991). Back when most synthesizers utilized one main configuration of oscillators, envelope generators, and filters to produce all their sounds (which is still largely true of many synths today) the idea was to make a synthesizer in which its individual building blocks could be changed and/or connected in different configurations (which they call Algorithms). This, of course, was not a new concept. Modular synthesizers have always had this flexibility. But the problem with modular synths is you have to patch each component manually, which not only takes time, but also requires a great deal of knowledge (experience) in predicting the outcomes. Kurzweil simplified the process by putting 31 useful algorithms under computer control and building the functionality to easily utilize them into their OS. VAST basically is all of those architecture choices as well as the ability to modulate their parameters from a wide list of control sources.That's the strict definition of VAST. As time went on, however, the concept of VAST began to encompass the many other unique aspects of the Kurzweil OS. Things such as Functions (FUNs), multiple LFOs, ADSRs, and Envelopes can all really be thought of as part of the VAST architecture since they provide unique and very powerful capabilities that are generally not found in most other synths on the market. Many soundware designers who've delved into the depths of VAST claim it is the most powerful overall synthesis engine on the market.Kurzweil now has a new and improved VAST in the works. Soon the K2600's VAST architecture will include over 100 unique synthesizer configurations. Given the astounding things that have already been done with the current version of VAST (anyone who's heard Daniel Fisher's Dark Side patch knows what we mean by astounding) there's absolutely no telling what will be possible with these new tools.

VFO
Abbreviation for Variable Frequency Oscillator: a somewhat generic term that can refer to all oscillators with variable frequency abilities. While the term can be used generically it tends to show up most commonly in radio transmission parlance. Radio frequency VFO’s are often used superheterodyne AM and FM tuners to produce waveforms that combine with the transmitted carrier as part of the reception process (see WFTD Heterodyne for more background). In music synthesis VFO’s are common, however, they tend to be referred to by more specific names that denote the method for changing the frequency, such as VCO (Voltage Controlled Oscillator) or DCO (Digitally Controlled Oscillator).

Virtual Analog Synthesizer
A digital synthesizer that mimics the circuitry found in an analog synthesizer. A Virtual Analog synth emulates analog characteristics by implementing mathematical models of analog circuitry. Analog modeling is a type of physical modeling, which imitates the electronic properties of circuit components rather than the mechanical or acoustical qualities of some device. It's important to understand that digital synthesizers as they are currently implemented don't exactly model the changes in voltage an analog synth uses to operate. Analog's voltage fluctuations are smooth, continuous and infinitely variable, and the interactions that take place between all the components under different conditions are highly variable and dynamic. Digital synths, on the other hand, represent signal changes as numbers. Digital signals and parameter values are quantized into a finite number of discrete steps. How these steps ultimately become manifested as an analog signal (or control how that signal is generated), and ultimately the quality of that signal, will depend upon the implementation of the software and the D/A converter at the end. Even where this implementation may be "perfect," and can produce a perfect replica of an analog signal at a moment in time under one set of conditions, it may fall short in the next moment under a slightly different set of conditions just due to the enormous complexity of all the possible variables of an analog system as the components interact with each other and the environment. In theory every signal aspect of a device's operation can be modeled, but in practice they are not and this is one place inaccuracies in the final result can creep in. There are many ongoing advances in this type of modeling so expect to see better and more realistic implementations in the future.

Wavetable Synthesis
A method of sound synthesis in which waveforms are generated by loading their characteristics from a special set of parameters stored in a lookup table in computer memory. Advanced wavetable synthesizers are able to crossfade between different waveforms while notes are sounding, which can produce very complex sounds. The resulting complex waveforms are often further modified by other filtering techniques and envelope generators.

Z-Plane Synthesis
Z-Plane Synthesis is E-mu's proprietary technology for providing dynamic timbral control of sample-based waveforms. Conventional synthesizer filters consist of a single section that simply allows you attenuate a waveform's harmonic content above a single frequency with (in some cases) an optional resonant peak at that frequency. In contrast, a Z-Plane filter consists of seven sections, each (very much like a band of parametric EQ) allowing independent control of frequency, bandwidth and degree of peak or notch. As a result, Z-Plane Filters can model virtually any resonant characteristic; whether that of an acoustic instrument body, the human vocal tract or even something that does not exist in nature. This modeling capability alone makes Z-Plane Filters extremely powerful filters, but their real power comes from their ability to smoothly interpolate (or "morph") between resonant models. Whether in response to velocity, pressure, or a variety of real-time controls, Z-Plane filters let you dynamically transform sounds. Z-plane synthesis was first implemented in the Morpheus (the name has nothing to do with the figure from Greek mythology but refers to 'morphing', a term which means to change from one thing to another), and its use of interpolation between two filter shapes is very reminiscent of how the Fairlight 'merged' from one waveform to another. Extremely complex filter shapes are created through the use of up to eight filter components, each of which is comparable to the traditional low-pass, band-pass or high-pass filters or parametric equalizer bands. The resulting sculpting of the sound is far more precise and subtle than in any previous type of synthesis. In addition to the basic function of the filter, starting by removing the high and/or low end, peaks and notches can be placed at will anywhere across the entire audible frequency range. Along with being able to tailor the most precise filter responses ever, Z-plane synthesis is then able to interpolate smoothly between two of them. This not only allows the user access to a myriad of additional filter responses, if the filter is held static in any of the transition positions, but as the interpolation can be carried out in real time, radical changes in the filter response can be made in the course of a sound being played back, with the 'Morph' parameter enabling the user to change backwards and forwards at will between the starting and ending filter shapes. With Emu's long-established modulation matrix providing a host of possible controllers for this Morph parameter, these timbral changes can be controlled by anything from velocity, envelopes or wheels, through to custom Function Generators. Whilst this is all similar in concept to controlling the cutoff frequency of a conventional filter using an envelope or LFO, the actual results produced are far more striking to the ear. Surprising as it may seem, we still haven't scratched the surface of Z-plane synthesis. In fact, the basic Morph parameter on its own might be thought of as X-axis synthesis. Another parameter, Frequency Tracking, introduces the equivalent of a Y-axis into the equation. This is the closest parameter to the conventional filter cutoff, in that it moves the complex Morph filter up and down the frequency range. In combination with the Morph parameter, Frequency Tracking gives two-dimensional control over the filter shape. Unlike a conventional filter cutoff, though, the Frequency Tracking parameter cannot be moved in real time, but must be set at Note On (presumably because there has to be some limit on the processing power required). This makes it suitable for hooking to parameters like keyboard tracking and velocity, but unavailable for controlling from aftertouch or envelopes. However, the real-time Morph parameter allows much more radical effects than filter cutoff movement, and thus more than makes up for the fact that you have to fix the Frequency Tracking at Note On. We still haven't mentioned the 'Z' axis that completes Z-plane synthesis: a third parameter, Transform 2. The function of this varies from Z-plane filter to Z-plane filter, but one example of what it can do is increase the size of the peaks and notches in the filter contour (similar to the individual peak which is increased in a conventional filter by the resonance control). Now that we've introduced the Z-plane into the equation, we can begin to visualize the three-dimensional variations possible in the resulting filter contour. With Z-plane synthesis, we've started to touch on the technology used in physical modeling, which is currently where all the big strides in synthesis are being made.

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