Actually, no there isn’t a limit other than practicality. Common sense should be your guide here. If you start to get sluggish response you should probably put a limit on yourself. Can you run out of polyphony with a tone generator that has 128 note. Some people never will – others will run out no matter how many notes of polyphony they are given. It all depends on your understanding of how polyphony works and how to use it. For example, the sustain pedal – a curious device that only occurs on very few instruments in the real world…piano and harp come to mind. Beyond these two instruments sustain is accomplished only on self-oscillating instruments – where the musician continuously applies pressure to the driver. Judicious use of sustain pedal is always recommended with any synthesizer. If you are a piano player that leaves it down – you are a candidate for running out of polyphony