Alesis QuadraSynth Plus Reference Manual page 90

Editing Programs: Chapter 6
Sound Overlap (00 to 99)
This determines how many voices can overlap on the same pitch.
Example: If you hold the sustain pedal down and play the same
note over and over, Sound Overlap determines how many voices
are available for that note, and thus how many voices will
overlap (play simultaneously).
In the old days, different brands of synthesizers offered different
voice allocation schemes. One brand used a method called
"rotate mode" in which each time a note was struck, a new voice
was used. Another brand used a different method called
"reassign mode" whereby if a note is played and then played
again, the same voice is used both times. In other words, a new
voice is used each time a new note of a different pitch is played.
The Sound Overlap value lets you choose a comfortable setting
between rotate mode and reassign mode. When the value equals
99, you are always in rotate mode, using up polyphony; if the
value is 00, you are always in reassign mode, conserving voices.
Set the value anywhere between 00 and 99 and you will get a
combination of both, with partiality toward whichever mode the
value is closest to.
A piano sound requires some Sound Overlap, but not a lot; it
isn't natural to hear too many voices on the same note. On the
other hand, having only one voice per pitch isn't natural either;
let's say you played a loud note with the sustain pedal held,
followed by a soft note--the second note would abruptly cut-off
the first. On a real piano, the string would still be resonating
from the first (loud) note when the second (soft) note was
played; thus the two notes would overlap.
Sound Overlap is especially useful in Drum Mode. In Drum
Mode, each drum sound is designated to one note (or sometimes
a group of notes). When playing one note for a drum sound,
such as a snare, and you attempt to play a roll, the Sound
Overlap controls how much of an overlap will exist between
each pair of notes. If the Sound Overlap value is set low, you are
more likely to hear old notes getting cut-off.
This function has added value when the Program's Keyboard
Mode parameter is set to Mono, instead of Poly. When playing
monophonically, Sound Overlap controls the amount of overlap
between notes. Normally, even if the sound has a long release
time, playing a new note in Mono Mode will cut-off the previous
note. By adjusting the Sound Overlap value, you can still hear
the previous note fading away after the new note has been
played.
J
It is important to note that Sound Overlap can have a negative effect on
polyphony.
QuadraSynth Plus Piano Reference Manual 91