Yamaha MU80 Owner's Manual page 110

UTILITY MODE
EQ Lock
Receive General MIDI Exclusive (RcvGMExcl)
Receive System Exclusive (RcvSysExcl)
100
This determines whether or not the EQ settings of the MU80 are re-
set when receiving a GM System On or XG System On message.
If you want to keep the current EQ settings, set Mute Lock to on.
(This parameter has no effect in the Performance mode.)
This determines whether GM System On or XG System On messages
are received or not. The on setting allows these messages to be received.
This determines whether System Exclusive messages are received or
not. System Exclusive messages are data specifically (or "exclu-
sively") related to the MU80. The On setting allows these messages
to be received. This should be to On when receiving bulk data from
a MIDI data storage device. (See page 102.)