Umphrey's McGee

'Umphrey's McGee' is an American progressive rock jam band based in Chicago whose music is often referred to as "progressive improvisation."

Although the band is part of the jam-band scene, like Phish and the Grateful Dead (with ever-changing setlists, improvisation, two sets per night, open-taping policy, etc), they are much more influenced musically by progressive rock bands such as King Crimson, Yes, Pink Floyd, Dream Theater, Frank Zappa, and Genesis, as well as heavy metal bands such as Iron Maiden. The band also identifies The Police, The Beatles, and Led Zeppelin as primary influences.

From Wikipedia