Initially performing under his real name, Carel Hagemans was bassist and vocalist for a number of Dutch pop bands in the 1960s: Peter and the Beats (1965-66), The Heralds (1966-67), Spacial Concept (1967-68), and Big Wheel (1968-1969).

In 1969 he began to use the name Cyriel Havermans in live performances in the Netherlands with members of the nascent Focus (Thijs van Leer, Martijn Dresden, and Hans Cleuver) as his backing band.

His time as bassist with Focus lasted from late 1970 until September, 1971 during which time he played many live concerts with the group and recorded "Moving Waves". In 1971 this LP won the Edison award, the Dutch equivalent to the Grammy, for best album of the year. Aside from Cyriel's plaintive, wordless wailing on "Pupillae" from the "Moving Waves" LP's sidelong "Eruption" suite, his vocal talents found no other outlet on this mostly instrumental album.

He left the band to pursue a solo career playing melodic, acoustic guitar music with English lyrics. At this time Cyril dropped the 'e' from his first name. An eponymous album was released in 1973 with musical support from his old Focus bandmates Jan Akkerman, Thijs van Leer, and Pierre van der Linden. A second album, "Mind Wave", followed in 1974, and Cyril's group was sometimes featured as an opening act for some of Focus' European concerts in 1975.

He was a guest musician on Lucifer's "Margriet" album, released in 1977.