"Jam based music" is not defined by any music genre. It is a spontaneous production by musicians in performing their most creative expression of music. Sometimes, it is completely improvisational, or even avant-garde, while other times it follows a set theme around which the musicians present their individual interpretations. In America, it could be said that the Jam is derived directly from Bluegrass or Jazz. Indeed, many of Jerry Garcia's guitar riffs were influenced by familiar riffs from Bluegrass, and several songs performed by the Grateful Dead were based on Bluegrass standards. The sound became unique to The Grateful Dead when they mixed the Bluegrass with some R&B, Blues, and Rock 'n' Roll.

But that doesn't necessarily define the Jam. Quicksilver Messenger Service, an early Jam Band, played music that was derived mostly from Rhythm and Blues, while Frank Zappa and the Mothers of Invention definitely had a Jazz feel to their jams. Before Lynyrd Skynyrd, Southern Rock meant Jamming. Johnny Winter and the Allman Brothers Band drew largely from The Blues, while the Marshall Tucker Band presented Jams influenced by Country Music, Bluegrass, Jazz, Blues, and Rock 'n' Roll and somehow made it all work together. Little Feat also performed a very eclectic Jam, with emphasis more on the Rock 'n' Roll side.

If we count Bluegrass and Jazz as the first generation of the Jam, then the third generation came in the eighties and nineties, influenced heavily by the bands of the sixties and seventies. The Dixie Dregs, Widespread Panic, Blues Traveler, Dave Matthews Band, Leftover Salmon, Phish, String Cheese Incident, and others, all took what they learned from the Dead and the others and transformed it into their own unique signature Jam stylings. And, at the beginning of the Twenty- First Century, the Dead returned in the form of Phil Lesh and Friends and Bob Weir's Ratdog. The music never really stopped.

The Jam Band usually abides by the following "rules" to which there are always exceptions:

1. The Jam Band is not a group of musicians playing to an audience at a concert. It is, rather, the host of a party entertaining its guests.

2. The Jam Band never releases a studio album that gives an indication of what they do during their shows. There are, of course, some exceptions to this rule, but normally the Jam Band is about what they play live, not what is heard on the radio.
--A Jam Band never purposefully tries to produce a top ten recording. It happens by accident, but approximately 90% of those who go to a show to hear a song they heard on the radio will not return because...

3. The Jam Band never plays a song "just like on the record." In fact, the Jam Band never plays anything the same way twice, and...

4. The Jam Band never does what is expected. In fact, the Jam Band makes sure nothing is expected.

5. Cover songs can be performed even if the singer doesn't remember the words. The show is about the music, not the words.

6. "The Music Never Stopped"

7. Finally, the most important rule, Music is Spiritual.