QuoteI took a deeper look into the exported MIDI myself now and for what I can say, the issues I have here are the volume per note / delay and cut settings that just get "overwritten". The song is "compressed" to 4-rows/beat (its 8 in the .mptm) and especially the volume settings look quite different and "weird" in certain parts.
QuoteThey do reflect settings like "volume commands with note are velocities" (if I checked this option in the instrument panel) but the export gets it kinda wrong, muting the drums completely after a drum roll for example or setting the volume to a far to low value. Another issue is the mixing of instruments in the channels, drums are mostly effected by this and it kinda breaks things sometimes.This sounds like you mix and match between instruments with different volume command handling on the same MIDI channel. This is not a bug in the MIDI export per se; that's simply how OpenMPT's internal plugin architecture works. If one instrument modifies the MIDI channel volume, and another instrument is not configured to do so, then the second instrument will continue to use the MIDI channel volume set by the previous instrument.
QuoteIt would be cool, if OpenMPT could just send the notes with their commands straight to a (virtual) MIDI device, it would help figuring out what I'm doing wrong.The MIDI Input / Output Plugin does exactly that. In fact, this is the only way I can recommend writing a MIDI score in OpenMPT, because plugin-based instruments and MIDI export share identical behaviour, while sample-based instruments behave different in many ways (e.g. the MIDI volume command handling setting you found are specifically meant for plugins, not sample-based instruments, so you would have no way of judging their behaviour while working with sample-based instruments).
QuoteOr an option in the export to just parse the notes and commands as they are, without changing anything - even if this means the exported MIDI might not work at all and I've to figure it out myself what's going wrong.MIDI export really doesn't do much more than that anyway. If you don't set any specific MIDI volume command handling, it cannot affect the exported output, for instance.
QuoteTo be frank: does the export really work, or is it more of a "work-in-progress" feature that only gets developed when someone feels like it? More of a "nice-to-have-but-it-still-doesn't-work-as-intended"? (no offense meant)There may always be unknown issues, as well as known limitations (perfect MOD to MIDI conversions are simply not possible), but general, you won't find any half-finished features in OpenMPT. Either the feature is considered to be done or it's not released to the public.