Jam band

A jam band is a musical group whose concerts and live albums substantially feature improvisational "jamming". Typically, jam bands will play variations of pre-existing songs, extending them to improvise over chord patterns or rhythmic grooves. Jam bands are known for having a very fluid structure, playing long sets of music which often cross genre boundaries, varying their nightly setlists, and segueing from one song into another without a break. Originally emerging from the psychedelic rock movement of the 1960s, the style was pioneered by acts such as the Grateful Dead, the Free Spirits, Love, the Yardbirds, the Paul Butterfield Blues Band, the Mothers of Invention, Jefferson Airplane, Soft Machine, Cream, the Jimi Hendrix Experience, Pink Floyd and the Allman Brothers Band.