"Echoes" is one of Pink Floyd's extended compositions. On the album Meddle, it runs 23 and a half minutes; on the original LP, it took up all of side two. The group was known for lengthy, mostly instrumental works before, but "Echoes" was their longest yet. Its genesis occurred in January 1971, when Pink Floyd went into the recording studio and recorded a series of sound experiments informally dubbed "Nothing -- Parts One to Twenty-Four," culling some elements months later for a suite at first facetiously called "Return of the Son of Nothing," which began with a single piano note played through a rotating Leslie speaker (usually used with the Hammond B-3 organ). After that, the group mixed and edited together various pieces of music, also including three sets of imagistic lyrics sung by bandmembers David Gilmour and Rick Wright in a calm, gentle harmony style they would repeat on Pink Floyd's subsequent album, The Dark Side of the Moon. Other than that, "Echoes" had no unifying themes, instead weaving from one musical passage to another. "Echoes" was introduced in concert at Montreux, Switzerland, on September 18, 1971. Meddle was released October 30, 1971, and became a commercial success, selling over two million copies in the U.S. alone and reaching the Top Tive in the U.K. Pink Floyd performed "Echoes" in its concerts during the early '70s, including a filmed performance that turned up in the 1972 film Pink Floyd Live at Pompeii. They briefly reintroduced the song as the opening number on their 1987 world tour, but dropped it after the first few dates.