BTW..the polyphony is a sound generator limitation..the damper/hold pedal down will not allow any "new" voices...
If you hear a sound it is using polyphony..It is not a key pad issue..

Also keep in mind, more detailed sounds use a combination of tones/partials..as an example the Tyros uses 4 tones for many of the better sounds...each of these tones use polyphony[4 tones=4 polyphony for each key depressed]..