Yamaha MU90R Owner's Manual page 63

MULTI MODE
EG Decay Time
EG Release Time
5 4
Selected Part and MIDI channel
This determines the Decay Time of the EG, or how rapidly the
sound dies out as a note is held. For the Filter, this determines how
long it takes for the Filter effect to die out.
Selected Part and MIDI channel
This determines the Release Time of the EG, or how long the sound
sustains after a note is released. For the Filter, this determines how
long the Filter effect continues after a note is released.
Graphically shows EG Decay Time setting for each Part.
Graphically shows EG Release Time setting for each Part.