As the only original band member left, McGuinn elected to hire bassist John York as Hillman's replacement. York had previously been a member of the Sir Douglas Quintet and had also worked as a session musician with Johnny Rivers and the Mamas & the Papas. In October 1968, the new line-up entered Columbia Studios in Hollywood to begin recording the "Dr. Byrds & Mr. Hyde" album with producer Bob Johnston. The sessions saw the band juxtaposing their new country rock sound with more psychedelic-oriented material, giving the resulting album a stylistic split personality that was alluded to in its title. In the wake of the recent changes in band personnel, McGuinn decided that it would be too confusing for fans of the group to hear the unfamiliar voices of White, Parsons and York coming forward at this stage, and so they were relegated to backing vocals on the album. As a result, "Dr. Byrds & Mr. Hyde" is unique in the Byrds' back catalogue as McGuinn sings lead on every track.