This is a good question for the purchase of a digital piano. No matter how good your digital piano sounds or feels when you lose, take notes during the game. So, what is the number of notes of polyphony for you? Here's how to figure it out.
What do you want to use the digital piano?
If you need a digital piano that emulates an acoustic piano for simple practical purposes, you're probably fine with 32-voice polyphony. In the rare event that you start to loseNotes with the sustain pedal use, may not be able to notice. Algorithms using digital pianos, to determine which notes to fall when it reached the maximum number observed. Often states that could easily take the listener to remember without being eliminated. So the bad news is that when you reach max missed notes polyphony. The good news is that it can be noticed.
Sequencing and layering
If you think of different songs on your hard disk digital piano, go ahead and get amore polyphony. Every time you are on a different track of an existing line, it contributes the maximum polyphony. The digital piano is one of the previous track, as well as your current games, all on polyphony max. So if you start adding different sounds and voices of different tracks, you can see how fast you can reach a maximum polyphony of 32 at some point in the song.
Also, if you use lots of effects such as layering, then you get more than 32 voices of 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.