Abbey Road is the eleventh studio album by the English rock band the Beatles, released in 1969. The recording sessions for the album were the last in which all four Beatles participated. Although Let It Be was the final album that the Beatles completed before the band's dissolution in April 1970, most of the album had been recorded before the Abbey Road sessions began. A double A-side single from the album, "Something"/"Come Together", released in October, topped the Billboard chart in the US. Abbey Road is a rock album that incorporates genres such as blues, pop and progressive rock, and it makes prominent use of the Moog synthesizer and the Leslie speaker. Side two contains a medley of nine songs that has subsequently been covered by other notable artists. The album was recorded amidst a more collegial atmosphere than the Get Back/Let It Be sessions earlier in the year, but there were still frequent confrontations within the band, particularly over Paul McCartney's song "Maxwell's Silver Hammer", one of four tracks on which John Lennon did not perform. He had privately left the group by the time the album was released and McCartney publicly quit the following year. Although Abbey Road was an immediate commercial success and reached number one in the UK and US, it received mixed reviews, with some critics describing its music as inauthentic and bemoaning the production's artificial effects. Many critics now view the album as the Beatles' best and rank it as one of the greatest albums of all time. In particular, George Harrison's contributions, "Something" and "Here Comes the Sun", are considered to be among the best songs he wrote for the group. The album's cover features the four band members walking across a zebra crossing outside Abbey Road Studios and has become one of the most famous and imitated images in the history of recorded music. As of 2009, Abbey Road remains the Beatles' best-selling album.