Alesis QuadraSynth Plus Reference Manual page 91

Editing Programs: Chapter 6
If you have Sound Overlap set to 99, hold the sustain pedal and
play a series of notes, you will run through all 64 voices in no
time. By adjusting the Sound Overlap to a lower value, you
decrease the number of voices used by each new note, and
thereby ensure there are voices available to play other sounds, if
necessary.
QuadraSynth Plus Piano Reference Manual 92