EMI's policy of testing and customising new gear extensively before putting it into use. The Beatles recorded "Hey Jude" and "Dear Prudence" at Trident because it had an 8-track console. When they learned that EMI also had one, they insisted on using it, and engineers Ken Scott and Dave Harries installed the machine (without studio management authorisation) in Abbey Road's Studio 2. The band held their first and only 24-hour session at Abbey Road during the final mixing and sequencing for the album. This session was attended by Lennon, McCartney and Martin; Harrison had left on a trip to the US the day before. Unlike most LPs, there was no customary three-second gap between tracks, and the master was edited so that songs segued together, via a straight edit, a crossfade, or an incidental piece of music. Genres and length The Beatles contains a wide range of musical styles, which authors Barry Miles and Gillian Gaar view as the most diverse of any of the group's albums. These styles include rock and roll, blues, folk, country, reggae, avant-garde, hard rock, music hall and psychedelic music. The only western instrument available to the group during their Indian visit was the acoustic guitar, and thus many of the songs were written and first performed on that instrument. Some of these songs remained acoustic on The Beatles and were recorded solo or by only part of the group (including "Wild Honey Pie", "Blackbird", "Julia", "I Will" and "Mother Nature's Son"). Author Nicholas Schaffner views the acoustic slant as reflective of a widespread departure from the LSD-inspired psychedelia of 1967, an approach initiated by Bob Dylan and the Beach Boys and adopted in 1968 by artists such as the Rolling Stones and the Byrds. Edwin Faust of Stylus Magazine described The Beatles as "foremost an album about musical purity (as the album cover and title suggest). Whereas on prior Beatles albums, the band was getting into the habit of mixing several musical genres into a single song, on The White Album every song is faithful to its selected genre. The rock n' roll tracks are purely rock n' roll; the folk songs are purely folk; the surreal pop numbers are purely surreal pop; and the experimental piece is purely experimental." Martin said he was against the idea of a double album at the time and suggested that the group reduce the number of songs