There are at least six bands/acts called Zen. 1. Zen was a Dutch pop/rock band of the late 1960s, established in 1965 by by Siegfried 'Siebe' de Jong (vocals, saxophone) and Dirk van der Ploeg (guitar, vocals). They are almost exclusively known for their version of the theme song from the musical 'Hair', which made them the perfect 'one hit wonder' in early 1969. Recorded in late 1968, 'Hair' rocketed straight to #1 in the Dutch Top 40 in January 1969.