SPCs should auto-loop, as should most VGM tracks when the "Loop VGM Tracks" setting is checkmarked in the Settings tab.
Thanks so much for the reply. I've been waiting a while for someone to get back.
I don't see a Settings tab anywhere. This is what it looks like for me. (Windows 8 64-bit)
Unless there is some kind of tag in the actual music file itself, but I don't know where that is either.