 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 . 
