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. In 1974, Keizer joined BZN to replace their drummer, Jaap Sombroek. When the band's lead singer, Jan Veerman, left later that year Keizer replaced him.
In 2000, Keizer started his first French language solo album. Two more solo albums followed. Together with Jan Tuijp and Jack Veerman he owns a production company: JJJ Productions.
In 2007, he disbanded BZN. In 2008, he released another solo album Give me your smile. His sixth solo album Chords of Life was released in 2009.
In January 2010, he was on the jury for the TROS singing competition Sterren.nl Academy.