The Dutch band Focus was formed in 1969. After their debut album the line-up changed to Jan Akkerman, Cyril Havermans, Pierre van der Linden and Thijs van Leer. Their 1971 album 'Moving waves' included the song 'Hocus pocus', which would achieve international fame. The instrumental rock classic consists of Akkerman's guitar chord sequence used as a recurring theme, with interludes that include alto flute riffs, accordion, guitar, and drum solos, whistling, nonsensical vocals, falsetto singing, and yodeling.
Their third album 'Focus III' (1972) included the track 'Sylvia', written by Van Leer, which became a major hit in many countries including the UK, where it reached number 4. This single contains both tracks, which made number 9 in the Netherlands.