To improve the quality of a module file, there are many ways you can edit.

I'd like to write a tutorial on conversion - you will achieve surprising results that differ between each file type, but it will work to simply change the format in OpenMPT, Renoise or virtually any other cross-platform music tracker or sequencer.

Other than that, you can just edit the music directly to improve quality. For MIDI files, I recommend using a MIDI cable and an external synthesizer. You can't change the sound of the Windows MIDI synthesizer without breaking your PC, but you *can* apply edits and convert it to a module file, then save to make more edits.