Power trioThe power trio was a rock and roll format popular in the 1960s. The power trio has a lineup of guitar, bass and drums, leaving out the rhythm guitar of the classic rock quartet, which dates back to the blues bands of the 1950s. The rise of the power trio was made possible by developments in amplifiers and guitar technology that permit the lead guitar to provide more sound than before.
Models for the power trio include The Who, Cream, Led Zeppelin, and the Jimi Hendrix Experience, although none of these were ever particularly identified as power trios. (The Who and Led Zeppelin both had the power trio lineup, but added a vocalist as a fourth member.)
Notable power trios include Blue Cheer, Cactus, Glass Harp, Rush, and Mountain. Power trios were loud and went for long jams. Typically, vocals and songwriting were less important than overall impact. Compare, for instance, the Jeff Beck Group, with Rod Stewart on vocals with Beck, Bogart, and Appice, a similar lineup without a significant vocalist. The latter was called a power trio, but the Jeff Beck Group was not. The emphasis on guitar solos and crashing rhythm sections in the power trio contributed to the development of heavy metal.