I like to use Synthesia to play back MIDI files with my keyboard's built-in MIDI synthesis.
- OS: macOS Monetery 12.6.3 (Intel MacBook)
- Synthesia version: 10.9.5893
- MIDI interface: Steinberg UR22 mkII
- Keyboard: Yamaha PSR-350
Yesterday, I turned both of these options back on. I listened to a selection of General MIDI and Yamaha XG MIDI files with these settings on and the results were pleasing.
But today, I opened Synthesia again and suddenly, all these songs which played fine yesterday with the same settings suddenly sound terrible, because every instrument is replaced with a piano voice! This happened both for General MIDI and Yamaha XG MIDI files. I was very confused.
So I tried disabling just SysEx messages again, and the all-instruments-are-pianos issue was gone, but those Yamaha XG MIDIs didn't sound as good, because I guess SysEx messages used for effects and so on were no longer getting through. I tried toggling the setting on and off, and every time I turned on SysEx messages, the problems returned.
I then of course tried restarting Synthesia, disconnecting and reconnecting my MIDI interface, and turning my keyboard on and off. None of these did anything to the problem.
After thinking about the problem a bit, I wondered if Synthesia was only sending a GM reset when the SysEx option was turned off, for some reason. I found out about the secret settings area (hold Shift on start), and turned on GmReset. It did… nothing, so I turned it off.
I then tried turning on GsReset. That seemingly fixed the issue! But then I turned off GsReset, and the issue was still fixed! It's also very strange that this fixed things, because my keyboard's manual does not say anything about supporting the GS reset SysEx message, only the GM one.
Further experimentation suggests that's a red herring. It seems like there's a random chance that, when I start Synthesia, it will play back all instruments as piano, rather than with the correct voices?
Sorry I can't be more specific, I really have no idea…