Yamaha MU50 Owner's Manual page 105

UTILITY MODE
Mute Lock
Settings: off, on
Default: off
Receive General MIDI Exclusive (RcvGMExcl)
Settings: off, on
Default: on
Receive System Exclusive (RcvSysExcl)
Settings: off, on
Default: on
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This determines whether or not the Part Mute status of the MU50 is re-
set when receiving a GM System On, XG System On or Disk Orches-
tra On message. Generally, this message is automatically transmitted
to the MU50 as part of General MIDI song data. When Mute Lock is
set to off, this resets the Mute status of the Parts on the MU50. If you
want to keep the current Mute settings and disable this reset, set Mute
Lock to on. (For more information on the Mute function, see page 23.)
This determines whether GM System On, XG System On or Disk Or-
chestra 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 "exclusively")
related to the MU50. The On setting allows these messages to be re-