“Monophony,” “paraphony,” and “polyphony” – sounds like three characters from Greek mythology. But they actually are terms used to describe the total number of notes a synthesizer can play at once. Due to a recent analog synthesizer renaissance, questions about the meanings of these terms are more common than ever.
Monophony
Not including large modular synthesizers, the first “commercial” synths that bowed in the early ’70s could play only one note at a time. To confuse the issue, that one note could typically be made from one, two, or three oscillators. So, even though you could press one key and hear three distinct pitches, it was still considered monophonic (one note) because you couldn’t press a second key and hear three new pitches while the original three were still playing. This was the basis for most lead synth sounds, bass synth sounds, and various 2- or 3-note intervals that could be played across the keyboard. If you had an arpeggiator, then you could have that one note run up and down all the notes you were holding.
Paraphony
Paraphony is basically a hack that lets you play two separate pitches (and sometimes more on certain synths), but the stone-cold reality is that all the notes typically run through the same filter and amp, which means that they all share the same filter envelope and amp envelope. So even though you can control more than one pitch at a time from the keyboard, they all tend to attack and decay as a single unit.
Polyphony
Polyphony is the ability to play multiple, distinct notes, each with its own filter and amp envelope. Some early synths allowed two distinct notes at once (sometimes called “duophony”), which then blossomed to five (with the Sequential Circuits Prophet Five) and six notes (with the Korg PolySix). This made it possible to play a bass line with your left hand while playing chords or a lead with your right hand. At first, you might think that you’d never need more than five notes of polyphony if you’re only playing one note with your left hand and one to four notes in your right hand. While that can be true, more often than not, you’ll want the old notes to continue fading away while your new notes are playing — and fading notes count just as much as new notes.
Now that analog synths are, once again, almost as common as digital synths, it’s worth examining the differences in their polyphony. Many analog synths were (and are) monophonic. This is because an analog synth requires all the audio components to be duplicated every time there’s an additional note of polyphony. This makes it impossible — or at least impractical and unaffordable — to have the same polyphony counts that are relatively easy for digital synths. (Digital synths often have polyphony counts ranging from 16 voices to up to 256 voices.)
How Much Do You Need?
So, how much polyphony do you need? If you’re just doing bass lines or lead lines, then you can get away with a monophonic synth. If you only need to play simple chords that don’t have long release times, then you may be happy with four to eight voices. Longer, ambient performances may be easier to accomplish with 12 to 16 voices. But if you’re playing multiple tracks of complex parts, each using many notes, then you should focus on digital synths that have 64, 128, or 256 notes of polyphony. And there’s no problem at all with having both monophonic and polyphonic keyboards. They each have their own advantages!