Sustain version one, version two.
WAY back in early 80's Yamaha had the keyboard line, CS80, CS60 and the CS40. A classic keyboard for sure! Just listen to the band UK's first album, and the tune, ALASKA!
Anyway there were two switches labeled sustain 1 & sustain 2. The differences were while sustain 1 worked the way it usually does, but sustain two would sustain the chord, and while holding the pedal down and not lifting your foot, move to a new chord it will stop holding that chord and play the next won with no sustaining between the two. Great stuff.