Thijs van Leer on keyboard and flute and guitarist Jan Akkerman were at the heart of 70s Dutch rock band Focus founded in 1969. Their second album Moving Waves was released in 1971 and made an international hit of the band largely on the strength of the single Hocus Pocus.
Focus would release 6 more albums in the 70s while going through a series of line-up changes. Akkerman, for example, left in 1976. Five more LPs were released between 1985 and 2006 but none ever enjoyed the success of 1971's Moving Waves. Their 1973 live album At The Rainbow does come a close second.
Here's a live performance of Hocus Pocus from 1973. It's got everything: smart guitar riffs, drum and flute solos and...yodelling! I love it.