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 three were all veterans of the Chicago music scene, the group based itself in the San Francisco area. Bloomfield, Goldberg, and Gravenites were in turn bolstered by a rhythm section of bassist Harvey Brooks (who had played on some of Bob Dylan's mid-'60s records) and drummer Buddy Miles; on top of them came a horn section.