'n' roll group could do them justice, particularly through the desensitising wall of the fans' screams. 'Live Beatles' and 'Studio Beatles' had become entirely different beasts." The band's concert at San Francisco's Candlestick Park on 29 August was their last commercial concert. It marked the end of four years dominated by almost non-stop touring that included over 1,400 concert appearances internationally. 1966–1970: Studio years Sgt. Pepper's Lonely Hearts Club Band Freed from the burden of touring, the Beatles embraced an increasingly experimental approach as they recorded Sgt. Pepper's Lonely Hearts Club Band, beginning in late November 1966. According to engineer Geoff Emerick, the album's recording took over 700 hours. He recalled the band's insistence "that everything on Sgt. Pepper had to be different. We had microphones right down in the bells of brass instruments and headphones turned into microphones attached to violins. We used giant primitive oscillators to vary the speed of instruments and vocals and we had tapes chopped to pieces and stuck together upside down and the wrong way around." Parts of "A Day in the Life" featured a 40-piece orchestra. The sessions initially yielded the non-album double A-side single "Strawberry Fields Forever"/"Penny Lane" in February 1967; the Sgt. Pepper LP followed with a rush-release in May. The musical complexity of the records, created using relatively primitive four-track recording technology, astounded contemporary artists. Among music critics, acclaim for the album was virtually universal. Gould writes: In the wake of Sgt. Pepper, the underground and mainstream press widely publicised the Beatles as leaders of youth culture, as well as "lifestyle revolutionaries". The album was the first major pop/rock LP to include its complete lyrics, which appeared on the back cover. Those lyrics were the subject of critical analysis; for instance, in late 1967 the album was the subject of a scholarly inquiry by American literary critic and professor of English Richard Poirier, who observed that his students were "listening to the group's music with a degree of engagement that he, as a teacher of literature, could only envy". The elaborate cover also attracted considerable interest and study. A collage designed by pop artists Peter Blake and Jann Haworth, it depicted the group as the fictional band referred to in the album's title track standing in front of a crowd of famous people. The heavy moustaches worn by the group reflected the growing influence of hippie style, while cultural historian