In basic terms, polyphony describes how many notes an electronic instrument can play at any one time.
Why would you need more than 10 notes of polyphony? You only have ten fingers, right?
Yes, but you also have a sustain pedal and the potential for many notes to be sounding at once.
All instruments, from basic home keyboards to advanced digital pianos, will display this number somewhere in their specifications, and it is one factor that’s very important to look at when choosing an instrument.
For digital pianos, where realism is of paramount importance, polyphony is one factor that, if not high enough, could seriously degrade the playing experience.
A quick scan of a range of instruments from various manufacturers (including Casio, Yamaha, M-Audio, Korg and Roland) shows a number ranging from 32 to 128 or more.
Even a rudimentary knowledge of piano playing will tell you that an instrument with 128 notes of polyphony will allow for a greater range of playing styles and techniques than one with 32.
What happens if an instrument ‘runs out’ of notes whilst it’s being played? Simple. It stops sounding notes that have already been played.
How it calculates which notes to drop depends on how it has been designed. Some simply drop the earliest notes, others calculate which would cause the least harmonic disruption.
Generally, higher polyphony is one factor that will push up the price of an instrument, but it is definitely not something to skimp on. You may find an instrument that sounds and feels wonderful, but when you play a run of notes with the sustain pedal held down, you hear an ugly set of cut off notes as the instrument attempts to sound everything you play.
Particularly if you are intending to play more advanced classical and jazz pieces, you will appreciate a higher polyphony count.
I personally would not choose any instrument with less than 64 notes of polyphony – and ideally 96 or more.
Believe me, a lack of polyphony is very easy to hear, so don’t overlook this factor.