Chaky2: Microsoft GS Wavetable doesn't work, giving that error message, but "Microsoft MIDI mapper" does work. I don't know about giden's gallery, though.
If I remember correctly, the default value for MIDI in .ini file is "MIDI Mapper" (without "Microsoft") which gave me a blank list in MIDI devices selection in game config menu.
Truth be told, I first changed it to "MIDI Parser", and that's when I got the choices shown in config menu between MS GS Wavetable and MS MIDI Mapper, which are essentially the same.
Giving that I'm running it on Windows 7 (that all but dropped the support for MIDI alltogether), it is a full success to have MIDI ingame at all.
Edit:
I have a Realtek soundcard (embedded) and absolutely no MIDI drivers installed. All the MIDI I'm getting is software-based, which Microsoft GS Wavetable essentially is since DirectX 7.
yes thats right the microsoft GS wavetable doesn't work, in the past players had that selected & when they activated the midi in overseer thats when the error message arose.
I had been telling people for years that they had to mute the midi & then I found out it would work after I installed a creative card. All of a sudden midi mapper appeared in the configuration. I could never get it going with my realtek on board sound but I noticed the other day I have another pc with no creative midi drivers & the midi mapper showed up.
I found also downloading the midi mapper for vista/win 7 helps
Ps the midi crashing is only with the GS wavetop selected.