This is a good question to ask when considering buying a digital piano. It doesn't matter how good your digital piano sounds or feels if you keep losing notes during play. So what's the polyphony note count for you? Here's how to figure it out.
What are you going to use the digital piano for?
If you need a digital piano that emulates an acoustic piano for simple practice purposes, then you'll probably be fine with 32 note polyphony. In the rare case that you start losing notes with sustain pedal usage you may not be able to notice it. Digital pianos use algorithms to determine which notes to drop off if the max note count is reached. Often times they will pick notes that could be dropped without the listener easily noticing. So the bad news is if you reach your max polyphony you will lose notes. The good news is that you may not notice.
Sequencing and Layering
If you are going to record multiple tracks on your digital piano go ahead and get a higher note polyphony. Every time you add another track on top of an existing track, you are contributing to the maximum polyphony. The digital piano counts the prior track, as well as your current playing, all toward the max polyphony. So if you start adding different tones and voices on multiple tracks you can see how quickly you could reach a max polyphony of 32 at some point in the song.
Also, if you like to use layering effects a great deal, then get more than 32 note polyphony. The layering effect allows multiple voices / tones to play for every key stroke. If you have a grand piano and string effect on, every time you press a key it will use one note of your total polyphony for the grand piano tone and one note for the strings. This, in a sense, halves your total polyphony count.
Under these circumstances, get a higher than 32 note polyphony. You can find 128 note polyphony digital pianos for very affordable prices.
A Quick Note About Stereo
Some of the tones / voices on a digital piano may be in stereo. This means one note may have two different sounds recorded that play at the same time to emulate the sound of an acoustic. When this happens you are using up 2 notes of your polyphony for every key you hit, instead of one. This will in effect turn a 32 note polyphony keyboard into a 16 note polyphony keyboard. This will only happen on those effects that are in stereo.
A Good Polyphony Test
If you are worried about losing notes when using the sustain pedal try this. Hit the two lowest A notes on the digital piano. Hold them with the sustain pedal and do a glissando with both your hands. You shouldn't lose the two low A's if the digital piano uses an algorithm to drop off some of the notes in the glissando. You probably won't notice you're losing notes in the glissando. It's best if you don't lose the low A's, but if you do lose them on your digital piano that's not the end of the world.
Think of it like this. During regular piano play, if you ever get to the point where you reach your max polyphony count it will probably only happen for a few seconds. So it's not going to happen throughout much of your song. Which means you won't lose many notes.
But if you're getting a new digital piano and can avoid this, by all means do so. Digital piano prices are affordable enough nowadays that you can get a high polyphony count for a good price. Even some of the low end models are coming with a minimum polyphony of 64. Just use your own judgment when determining if it's necessary to pay the little extra for a higher polyphony capability.
