Just thought I'd share this slow blues jam track in G - it's great for letting it aaaaaall out and just tearing your instrument apart and/or playing really subtle phrases as well...
It's a basic 12-bar blues form all the way... backing track starts at 2:00!
Oh and for more jam tracks in G major, there's also
Fast Blues in G http://goo.gl/HpviWa
Deep Groove Blues in G http://goo.gl/8g5xrY