I was recently discussing a project over on byuu's message board to develop a standard distribution format for MSU-1 game packs to simplify life for the end users, especially given the differences between the various implementations (manifests or not, track-#.pcm vs romname-#.pcm, etc), along with a utility to extract the files and rename them properly for each implementation. As it turns out, the distribution format that they settled on is nearly identical to the existing msu-zip support already added to Snes9x (it's basically just a zip file with a custom file extension), except using the higan naming scheme for the files within the archive, and with the addition of a patch file inside the archive so the MSU-1 patch can be distributed along with the audio and data files. I had the idea that since this format was nearly identical to the .msu.zip support already added by OV2, I could add support for it as well here. I've already implemented it in the msu-zip branch here: f8da152 and am looking for feedback before merging it into master.

For a test, you can try the Conker's High Rule Tail pack here: http://www.mediafire.com/?qasv12obaaob49b

Usage:
-Download the test build here: https://dl.qwertymodo.com/snes9x-mercurial.zip
-Download the .msu1 pack from the link above.
-Acquire a copy of Zelda A Link to the Past (unheadered) and rename it "Conkers High Rule Tail (v1.2.3).sfc" to match the .msu1 file, and copy it to the same directory.
-Load the ROM file as normal.