Hmmm so your exporting to Midi? and you say that your music tool is not producing good quality MIDI?
Anvil Studio is probably the best midi editor I know of!
that should improve the quality
.
On the other hand you may want to know a little more about midi as it doesn't quite conform to most other formats.
Well you see MIDI is not like any other format, a MIDI recording is not recorded in wavelengths but in Music Notes that the Computer reads and plays the music on whatever Synthesizer the computer is set to, On most Windows computers the synthesizer Microsoft GS Synth built into their copy of Windows.
MIDI can't run on Linux unless you manually install a synthesizer onto your Linux computer, but I myself don't know how to install a synthesizer myself.
If you want your game to be universal on all Operating System I suggest you use a DAW and export to ogg.
Now I may sound like I know it all but you may want to do your own research on this subject as my knowledge
may be a little inaccurate