I'm trying to create a new SOUN resource with the ROL signature. I wrote a tool which creates the expected header for a MIDI file. The problem I encounter with MIDI files other than those extracted with Scumm Revisited is, ScummVM plays them like expected, but the native SCUMM exe does not. There is just nothing on the MIDI port at all.
I'm not even trying to do neat iMuse tricks or such. Just playing a single track/multi channel MIDI with startSound()
If you like to try for yourself, here is the tool: mid2rol.exe
It takes one parameter, which is the name of a single-track-MIDI-file. The output file is named 000_ROL.dmp and it is always mode 2, like all SCUMM MIDI files.