TG-300 is the SC-55 GS compatible mode. Most MU units will auto select XG mode for midis with true GM Reset messages. I have no experience with the MU50 though. Try adding a proper GM Reset sysex message to the start of your MIDI files.

I just tested this with my own MU50 and it doesn't auto-switch to TG-300 mode. I tested it with X-Wing, Master of Magic and Warcraft using standard GM settings.

What games are you seeing the switching behavior with?

I also looked up in the manual is there is nothing in there about auto-switching to TG-300 mode. Though the manual does state that if an XG init message is received, it will switch to XG mode automatically.

Shponglefan wrote on 2023-03-10, 02:39:

I just tested this with my own MU50 and it doesn't auto-switch to TG-300 mode. I tested it with X-Wing, Master of Magic and Warcraft using standard GM settings.

What games are you seeing the switching behavior with?

I also looked up in the manual is there is nothing in there about auto-switching to TG-300 mode. Though the manual does state that if an XG init message is received, it will switch to XG mode automatically.

When I installed the MU I had only Doom in that machine, so I thought it was something related to the module, but seems it is something related to the game that always force to TG-300 mode.

Tried in other games now and that doesn't happen.

The MU50 will switch operating modes based on reception of the following messages:

XG System On -> XG mode
GM System On -> XG mode (w/Bank Select and NRPN reception disabled)
GS Reset -> TG300B mode
Disk Orchestra On -> DOC mode

You can "lock" the unit to whatever mode it's currently in with the following System setting:

RcvGMExcl =off

If you're going to do this, I'd suggest performing some sort of manual reset before the start of each game, either physically, by switching from XG mode to one of the other modes and then back, or by sending a SysEx sequence instead:

F0 43 10 49 00 00 03 01 F7 ; RECEIVE GM ON (ON)
F0 43 10 4C 00 00 7E 00 F7 ; XG SYSTEM ON
F0 43 10 49 00 00 03 00 F7 ; RECEIVE GM ON (OFF)

Cloudschatze wrote on 2023-03-10, 04:15:

The MU50 will switch operating modes based on reception of the following messages: […]
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The MU50 will switch operating modes based on reception of the following messages:

XG System On -> XG mode
GM System On -> XG mode
GS Reset -> TG300B mode
Disk Orchestra On -> DOC mode

You can "lock" the unit to whatever mode it's currently in with the following System setting:

RcvGMExcl =off

If you're going to do this, I'd suggest performing some sort of manual reset before the start of each game, either physically, by switching from XG mode to one of the other modes and then back, or by sending a SysEx sequence instead:

F0 43 10 49 00 00 03 01 F7 ; RECEIVE GM ON (ON)
F0 43 10 4C 00 00 7E 00 F7 ; XG SYSTEM ON
F0 43 10 49 00 00 03 00 F7 ; RECEIVE GM ON (OFF)

Thank you very much! That's the trick! I think this solve this, and possible others issues.