complication, according to Harris, was that Clapton had become infatuated with Harrison's wife, Pattie Boyd, and adopted a heroin habit as a means of coping with his guilt. Overdubbing In Spector's absence, Harrison completed the album's backing tracks and carried out preliminary overdubs, doing much of the latter work at Trident Studios with former Beatles engineer Ken Scott. Harrison completed this stage of the project on 12 August. He then sent early mixes of many of the songs to his co-producer, who was convalescing in Los Angeles, and Spector replied by letter dated 19 August with suggestions for further overdubs and final mixing. Among Spector's comments were detailed suggestions regarding "Let It Down", the released recording of which Madinger and Easter describe as "the best example of Spector running rampant with the 'Wall of Sound, and an urging that he and Harrison carry out further work on the songs at Trident because of its 16-track recording desk. Spector also made suggestions about overdubbing more instruments and orchestration on some tracks, but encouraged Harrison to focus on his vocals and avoid hiding his voice behind the instrumentation. John Barham's orchestrations were recorded during the next phase of the album's production, starting in early September, along with many further contributions from Harrison, such as his lead vocals, slide guitar parts and multi-tracked backing vocals (the latter credited to "the George O'Hara-Smith Singers"). Barham stayed at Friar Park and created the music scores from melodies that Harrison sang or played to him on piano or guitar. Leng recognises the arrangements on "pivotal" songs such as "Isn't It a Pity", "My Sweet Lord", "Beware of Darkness" and "All Things Must Pass" as important elements of the album's sound. According to Scott, he and Harrison worked alone for "weeks and months" on the overdubs, as Harrison recorded the backing vocals and lead guitar parts. In some cases, they slowed the tape down to allow Harrison to sing the high-register vocal lines. Spector returned to London for the later mixing stage. Scott says that Spector would visit Trident for a few hours and make suggestions on their latest mixes, and that some of Spector's suggestions were followed, others not. Spector has praised Harrison's guitar and vocal work on the overdubs, saying: "Perfectionist is not the right word. Anyone can be a perfectionist. He was beyond that ..." Harrison's approach to slide guitar incorporated aspects of both