on rhythm guitar, McCartney on bass, Harrison on maracas, and Ringo Starr on drums. Harrison then overdubbed lead guitar, treated with automatic double tracking (ADT) and fed through a Leslie speaker to enhance the sound, and Lennon added harmonium over the two bridges. McCartney played a piano part, although it was not retained on the finished recording. Vocals were added to the track at the group's next session, on 19 April. These consisted of Lennon's lead vocal and McCartney's high harmony part, and Harrison supplying a third voice over the bridges. Lennon's vocal was also treated with ADT. The song was mixed in mono for its US release on 12 May and in stereo on 20 May. It was subsequently remixed in mono on 21 June. Release and reception "Doctor Robert" was one of the three songs from the Revolver sessions, all written by Lennon, that were given to Capitol Records in early May 1966 for inclusion on the US release Yesterday and Today. In other countries, it appeared on Revolver, where it was sequenced as the fourth track on side two of the LP, between "For No One" and "I Want to Tell You". The album was released on 5 August, shortly before the Beatles commenced their final concert tour, in Chicago. Author Shawn Levy describes Revolver as pop music's "first true drug album" rather than merely a "record with some druggy insinuations", and he attributes this especially to Lennon's contributions. In November, artist Alan Aldridge created a cartoon illustration of "Doctor Robert" and three other Revolver tracks to accompany a feature article on the Beatles in Woman's Mirror magazine. The illustration depicted Lennon dressed in a black cape that was partly drawn aside to reveal a set of shiny surgical instruments, although Aldridge's original design – which was overruled by the magazine's management for fear of offending potential advertisers – instead showed human limbs hanging inside the cape. Impressed with the artist's work, Lennon bought the original picture and proudly displayed it at his home. According to Aldridge, Lennon told him that he had "got it wrong, though" in depicting Dr Robert as a physician concerned with the human anatomy; instead, he was a "New York doctor who sold speed". In his review of Revolver, Stephen Thomas Erlewine of AllMusic calls "Doctor Robert" Lennon's "most straightforward number" on the album, when compared to his other Revolver compositions "And