...I'm thinking more about things for backing tracks or jamming w/live guitar, as opposed to loopy/DJ stuff like Reason.

I was talking about music sequencers earlier and I realised I have no idea what software is out there anymore? I used Cubase in college, which I mostly hated despite being good with it and I understand not that much has changed on the sequencing side. Emphasis on ease & fun, this will be purely messing around in my spare time.

I think there used to be a program Jambox or something but I can't find it through searching? Plus I'd be surprised if this thread hasn't been done before.

I use Magix Music Maker, but I doubt that's what you're looking for.