When guitarist Mike Bloomfield left the Paul Butterfield Blues Band in 1967, he wanted to form a band that combined blues, rock, soul, psychedelia, and jazz into something new. The ambitious concept didn't come off, despite some interesting moments; maybe it was too ambitious to hold all that weight. Bloomfield knew for sure that he wanted a horn section in the band, which he began forming with a couple of friends, keyboardist Barry Goldberg and singer Nick Gravenites. Although the trio were all veterans of the Chicago music scene, the group based themselves in the San Francisco area.