Until recently I didn't even know that such a genre existed. Then I came accross such cool groups as String Cheese Incident and Phish and realised that the 'jam band' is now a well established musical idiom. The Grateful Dead supposedly triggered the genre's evolution with their extended live and studio recorded jam sessions in the 70s. Does anyone of any others?
Yeah this is true, their music is very much based around improvisation. Although Zappa is in a league of his own! I know what you mean about that certain type of jam band (SCI, Phish etc.). Its fun to listen to but maybe it can be self indulgent? I'm not sure, i'm still deciding!
The Alman Brothers are very enjoyable live and play looooonnnng sets...or at least they used to. It's been awhile since I've seen them, but a 40 minute-long version of Whipping Post is worth the price of admission.
moe. is one of my favorites along with of course the Dead. Umphrey's Mcgee isn't too bad. I like the Disco Biscuits and Perpetual Groove as well. I wish I had made it to the 2006 Lollapalooza which featured an all jam band line-up. Yeah String Cheese Incident and Phish are faves as well. Haven't heard too much Keller Williams but he can jam. Have to sit down when I'm not writing and give him a listen.