From this thread:
...if there’s a particular song from a particular game that you want to use, depending on what that game is (and how much effort you put into making it work in-game) it may be possible to rip the music as a MIDI and port it yourself.
The most useful program for doing this is [VGMTrans](https://github.com/vgmtrans/vgmtrans). The following formats are compatible with VGMTrans:
...
Nintendo's SNES sequence and instrument format known as N-SPC (.spc)
...
You’ll notice that a fair number of them are listed as `(.spc)` . In this case, these are files ripped from SNES games. You can find large collections of them free to use (with credit of course) [here](http://snesmusic.org/v2/).
EDIT: The files you download from that site are .rsn files. These are archives and can be opened with 7-Zip or a similar program to access the .spc files within.```