Leader of the influential Dutch group ICP Orchestra. He had a profound effect on the country's music scene in the 1960s.
He worked with a wide range of musicians, drummers, bassists, and even his pet parrot.
His father Karel Mengelberg was a well-known and demanding Dutch conductor.
He was influenced by John Cage after hearing him lecture at Darmstadt where he became entranced with Cage's completely new, experimental style.