Keizer began his career in music as a drummer with the band Empty Hearts, which he renamed the Q-tips two years later, after the main guitar player left, and turned it into a close-harmony band.

By the late 1960s Keizer joined BZN to replace their drummer, Jaap Sombroek.

When the band's lead singer, Jan Veerman, left in 1974 Keizer replaced him.

[3] In January 2010, he was on the jury for the TROS singing competition Sterren.nl Academy.

[3] Since then, Keizer has reunited with BZN's singer Anny Schilder.