I do suggest Wine, actually. I've just ran Sekaiju with it and it happily played a random MIDI file I selected after changing the output port in settings to TiMidity++ (the first dropdown list in Setup->MIDI device and instrument->Midi out device). It probably also isn't just me, the latest appdb rating of Sekaiju is platinum on wine 4.0 - for the record, I'm using 5.20 staging.