The progressive-rock supergroup Emerson, Lake and Palmer were never really notable for their restraint, either in the complexity and execution of their music or in their over-the-top live shows.
Two-thirds of Emerson, Lake & Palmer have released a live album from their 2013 world tour.
The roots of progressive rock, or 'prog' if you prefer, was the seemingly natural outgrowth of psychedelia. Its roots can be traced back to the Beatles' wildly experimental studio adventures during 1966 and 1967. Bands took the ball from the Fabs and ran with it into previously unimaginable territory.