Thijs van Leer was born in Amsterdam in 1948. After studying art history at Amsterdam University, he went to the Amsterdam Conservatorium to study flute and composition.

He was guided in his flute by his father, a classical flutist, and he earned a degree in flute from the Geneva Conservatoire. He also took piano lessons, was coached in orchestral arranging by Dutch arranger/composer/conductor Rogier van Otterloo, and had organ lessons from Dutch organist/conductor Anthon van der Horst.

During his schooldays he led his own jazz group, playing the piano. His career began with the Ramses Shaffy cabaret group, doing close-harmony singing and playing flute. He then formed a trio that backed other artists and played solo, doing compositions of their own, as well as works by Traffic and the Canadian group The Collectors.

In 1969, after completing his musical education at the Conservatorium (Music Academy), the classically trained flautist sets up Trio with Martin Dresden (bass) and Hans Cleuver (drums). At the end of the year guitar virtuoso Jan Akkerman joins the band and its name is changed to Focus.

In 1972 Van Leer makes the solo album, Introspection, with instrumental music. The tracks are adaptations of classical melodies. The album is unexpectedly popular and remains in the charts for eighteen months. Van Leer is given a Zilversen Harp. Van Leer records several albums in the same style during the following years.

In 1978 Focus split up. Thijs van Leer and Jan Akkerman record a new Focus album in 1985, though the partnership soon goes wrong again.

In 2002 Thijs van Leer, Jan Dumée (vocals/guitar), Ruben van Roon (drums) and Bobby Jacobs (bass) perform under the name Focus. In April Roon is replaced by Bert Smaak (ex-Bots). The group tours the UK (Whitchurch Progrock Festival in August and Astoria Theatre with Caravan in November), the US (Classic Rock Festival, Trenton, New Jersey, with Uriah Heep, Asia and Nektar in October), Chile, Brazil, Mexico, Venezuela, Argentina and Peru. The CD Focus 8 is released worldwide in the autumn.