A disagreement between McCartney and his bandmates nevertheless resulted in McCartney walking out of the studio during the final session, for Lennon's "She Said She Said", on 21 June, two days before the band were due to fly to West Germany for the first leg of their world tour. The Beatles spent over 220 hours recording Revolver – a figure that excludes mixing sessions, and compares with less than 80 hours for Rubber Soul. Final mixing of the album took place on 22 June. The Beatles celebrated the project's completion by attending the opening of Sibylla's, a nightclub in which Harrison had a financial stake. Production techniques Studio aesthetic The sessions for Revolver furthered the spirit of studio experimentation evident on Rubber Soul. With the Beatles increasingly involved in the production of their music, Martin's role as producer had changed to one of a facilitator and collaborator, whereby the band now relied on him to make their ideas a reality. According to Rodriguez, Revolver marked the first time the Beatles integrated studio technology into the "conception of the recordings they made". He views this approach as reflective of the group's waning interest in live performance before crowds of screaming fans, "in favor of creating soundscapes without limitation" in a studio environment. For the first time at EMI Studios, the company's four-track tape machines were placed in the studio's control room, alongside the producer and balance engineer, rather than in a dedicated machine room. The Beatles' new recording engineer on the project was nineteen-year-old Geoff Emerick, whom author and critic Ian MacDonald describes as an "English audio experimentalist" in the tradition of Joe Meek. Emerick recalled that no preproduction or rehearsal process took place for Revolver; instead, the band used the studio to create each song from what was often just an outline of a composition. Speaking shortly before the start of the sessions, Lennon said that they had considered making the album a continuous flow of tracks, without gaps to differentiate between each song. The group's willingness to experiment was also evident in their dedication to finding or inventing sounds that captured the heightened perception they experienced through hallucinogenic drugs. The album made liberal use of compression and tonal equalisation. Emerick said that the Beatles encouraged the studio staff to break from standard recording practices, adding: "It was implanted when we started Revolver that every instrument should sound unlike itself: