Best remembered for their bizarre chart smash "Hocus Pocus," Dutch progressive rock band Focus was formed in Amsterdam in 1969 by vocalist/keyboardist/flutist Thijs van Leer, bassist Martin Dresden, and drummer Hans Cleuver. With the subsequent addition of guitarist Jan Akkerman, the group issued its debut LP, In and Out of Focus, in 1970, earning a European cult following thanks to the single "House of the King." Dresden and Cleuver were replaced by bassist Cyril Havermanns and drummer Pierre Van der Linden for the English-language follow-up, Moving Waves; the record generated the hit "Hocus Pocus," a hallucinatory epic distinguished by Akkerman's guitar pyrotechnics and van Leer's demented yodeling. Easily one of the flat-out strangest songs ever to crack the American pop charts, the single peaked at number nine in the spring of 1973, by which time Focus had already exchanged Havermanns for bassist Bert Ruiter and issued their third album, Focus III, which yielded the minor hit "Sylvia." In the wake of 1974's Hamburger Concert, the band streamlined the classical aspirations of earlier efforts to pursue a more pop-oriented approach on records like Ship of Memories and Mother Focus; though roster changes regularly plagued Focus throughout the period, none was more pivotal than the 1976 exit of Akkerman, who was replaced by guitarist Philip Catherine for 1978's Focus con Proby, cut with British pop singer P.J. Proby. Focus then disbanded, with the original lineup reuniting in 1990 for a Dutch television special.