 It showcased the band exploring progressive rock with jazz fusion and classical music elements with extended pieces and lengthy solos.Akkerman changed his sound, moving from a Gretsch White Falcon to a 1957 Gibson Les Paul Custom which enabled him to "'sing' on the guitar" to compensate for the group's weak vocals.Its opening track, "Hocus Pocus", became one of the band's best known tracks, featuring a recognisable rock guitar riff and van Leer's yodelling, whistling, and nonsensical vocals that developed through an improvised jam session.