In late 1964, Joe Boyd, an aspiring producer and friend of Elektra house producer Paul Rothchild, told Rothchild that the "best band in the world was on stage at a blues bar in Chicago". Rothchild took a plane to Chicago to see the Butterfield quartet, and later the same night went to a different club – again, at the suggestion of Joe Boyd – and saw guitarist Mike Bloomfield with a different band. According to Rothchild, it was at his impetus that Paul Butterfield hired Bloomfield as his second guitar alongside Elvin Bishop; Joe Boyd says that it was his idea. The Butterfield rhythm section of Jerome Arnold and Sam Lay had been hired away from Howlin' Wolf.
Sessions were arranged for December 1964, but these were abandoned for live recordings from the Cafe Au Go Go in New York City after the band's appearance at the Newport Folk Festival. The earlier studio recordings were eventually released on The Original Lost Elektra Sessions in 1995. Upon hearing the live tapes, Rothchild remained dissatisfied, and the band went into the studio in September 1965 in an attempt to record the album for the third time. The guitar solos were all played by Bloomfield, Bishop relegated to rhythm guitar. Keyboardist Mark Naftalin was drafted in at the September sessions and asked to join the band by Butterfield, expanding it to a sextet.