To any JCS users out there who happens to wander by this post: Please do NOT use only Sonic tracks for the rest of the levels you make.

And now, against all odds, a link to easily the best Sonic-music-in-mod-format collection I've ever found, ever: click.

As far as I can tell, for all the individual files you have to remove the ".gz" extension from the filename when you download. I was compelled to download all the tracks in the .tar file at the bottom (15MB) since I couldn't pass up such an opportunity.