Yamaha QY100 Owner's Manual page 52

Reverb block
parameter
parameter. This parameter allows you to select a specific block to
be turned on and off by the [AMP SIMULATOR] button on the top
panel, or a footswitch connected to the rear-panel FOOT SW jack
(when the footswitch is assigned to amp simulator section
switching via the UTILITY parameter described on page 245).
There's also an "ALL" setting which allows all blocks to be turned
on or off. When the selected block(s) are bypassed (off), the indi-
cator to the right of the [AMP SIMULATOR] button will go out).
On/Off parameter
52
For Singers: Cool Vocal Processing
The "On/Off" Parameter
At the very bottom of the parameter list is the "On/Off"
The settings are:
DLY
CHO
REV
ALL
The footswitch or [AMP SIMULATOR] button turns
only the Delay block on and off.
The footswitch or [AMP SIMULATOR] button turns
only the Chorus block on and off.
The footswitch or [AMP SIMULATOR] button turns
only the Reverb block on and off.
The footswitch or [AMP SIMULATOR] button turns all
three blocks — Delay, Chorus, and Reverb — on and
off.