[QUOTE=Zsofia]
Can somebody cure my ignorance and explain just exactly what a jam band is? I’ve heard the term before but have never been really clear on it.
[/QUOTE]
“Jamming” is the term musicians use for an informal get together in which musical ideas are shared and musical output is heavily improvised. A typical jam most musicians would be familiar with is a blues jam. Get a bunch of musicians together, yell out “OK, 12-bar blues in A” and everybody will just start playing. If you want to be more precise, you might specify the “turnaround” or other alterations to the progression, but musicians will pick up which version of the blues progression you want to play after the first go-round.
Now, in a rock context, a lot of times musicians will just get together and say, “hey, I got this cool riff/chord progression, let’s jam around it and see what happens” and will hope to develop new musical ideas by playing off other musicians and the such. A jam band is a band that takes this sort of improvisatory approach to playing (and usually composing) music. Extended improvisations are required in a jam band. A jam band is known for long form songs and will take a song that might be 3 minutes in the pop idiom and extend it out to 10, 15, 20 or so minutes. Jam band songs are not always this long, but the emphasis is on instrumental improvisation, not on tight songwriting.
As for jam bands, I don’t like them in general, but I do like some early Phish, Blues Traveler (which I consider a borderline jam band at most) and, of course, the Allman Brothers.