Kraftwerk's self-titled 1970 debut album employs organ clusters to add variety to its repeated tape sequences. In 1971, critic Ed Ward lauded the "tone-cluster vocal harmonies" created by Jefferson Airplane's three lead singers, Grace Slick, Marty Balin, and Paul Kantner. Tangerine Dream's 1972 double album "Zeit" is replete with clusters performed on synthesizer. In later rock practice, the D add9 chord characteristic of jangle pop involves a three-note set separated by major seconds (D, E, F), the sort of guitar cluster that may be characterized as a harp effect. The Beatles' 1965 song "We Can Work It Out" features a momentarily grating tone cluster with voices singing A sharp and C sharp against the accompanying keyboard playing a sustained chord on B to the word "time." The Band's 1968 song "The Weight" from their debut album "Music from Big Pink" features a dissonant vocal refrain with suspensions culminating in a 3-note cluster to the words "you put the load right on me."