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Microphone Month 5

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.

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