Just a small update. A user on github has found a few small issues with the audio re: clipping/distortion, and therefore I've been working with him on a script to (as an *optional* installer checkbox) globally lower the volume of the PCMs, by about 7.5dB (though in some cases less). From his testing this seems to have the music volume better match with that of sound effects ingame. However, he's using lr-snes9x, and I've not had the chance to test this in Higan (and have heard Higan handles volume somewhat differently than other MSU-1-capable emulators/devices), which is why I'm making this optional.
The next major version of the installer will include this option, some new alternate sources for a few songs, an adjustment to OCR track 76, and the requested ability to choose one of the premade selections of tracks as a "template" when picking a custom selection.