Enhanced Sidplayer is an editor to create .MUS files with. There is also a Stereo Sid editor that requires the Enhanced Sidplayer to install itself (or did originally). These were the most popular music format on the C64 if you want to use them under VICE.
Sidplayer is not a tracker file format but is simple to learn. I've written several SIDs but when Q-Link shut down and its equipment became America Online I kind of quit the SID scene also. I liked .MUS files better than AHX/Hively Tracker, though.
