Presets compare analogical to the one implemented in the Moog Subsequent 37
Quote from the manual of "Moog Subsequent 37"
COMPARE
This button allows you to load an existing preset without discarding any changes you have made to a current sound.
To alternate between a stored preset and a currently modified sound simply press the COMPARE button.
When the COMPARE button is illuminated, you are listening to a stored preset and no changes can be made to the sound.
When in this mode you can, however, audition different presets without discarding your currently modified sound.
