Yamaha RM1x Owner's Manual page 149

Wet sound: The audio signal that is processed by an effect. Nor-
mally when using an effect, not all of the audio signal is
passed through the effect. Rather, the degree of the effect is
adjusted by mixing the sound that passes through the effect
(the wet sound) with the sound that bypasses the effect (the
dry sound).
X
XG:
A tone generator format developed by Yamaha which expands
the GM specification to provide the richer expressiveness
and upward data compatibility that is demanded by today's
more sophisticated computer peripheral environment.
4. Glossary
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RM1x SEQUENCE REMIXER