JuceOPLVSTi VS geonkick

Check this out https://github.com/bsutherland/JuceOPLVSTi

A workaround is to not use OpenMPT's built-in OPL samples, but instead, an OPL VST instrument plugin like JuceOPLVSTi, and make your OPL instrument use this plugin instead of the OPL samples. Then you can either apply the reverb plugin to the channel you want, or just route the output of the OPL plugin to the reverb plugin.

JuceOPL — a clean FM/additive synthesizer.

I don't think the Volca FM would be a good choice for that. For a start, it can only play one instrument at a time (no drums/bass/chords playing alongside the melody). The sequencer is only 1 track and 16 steps. If you want to spend some of your time instead of money, you could try getting more acquainted with Ableton of FL Studio and use a free VST like JuceOPLVSTi.

I ended up using https://bsutherland.github.io/JuceOPLVSTi/ since it made composition way easier than messing around with tracker software. I haven't really looked into extracting the patches from the game, but i'm sure it's possible - it did have a jukebox mode after all.

I'd add Geonkick to the drums (it's a drum-synthesizer). Also, I'd add Galactic (from the excellent Airwindows -collection) and Aether to the Reverb-section.