Yamaha MU50 Owner's Manual page 47

MULTI MODE
Expression (Expresn)
Graphically indicates current Expression setting.
Pan
Graphically indicates current Pan setting.
Reverb Send (RevSend)
Graphically indicates current Reverb Send setting.
NOTE
Keep in mind that the Reverb effect must be properly enabled and set for this parameter to
work as intended. (See page 86.)
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This determines the Expression setting for the selected Part's Voice.
This determines the stereo position of the selected Part's Voice. A
setting of "Rnd" (Random) randomly assigns the Voice to a pan po-
sition. This is useful when you want to have different Voices sound
from different random parts of the stereo image.
This determines the level of the selected Part's Voice that is sent to the
Reverb effect. A value of 0 results in a completely "dry" Voice sound.