Cosaert studied violin and organ at the conservatory in Kortrijk and earned a degree in musicology from the Catholic University of Leuven with a thesis on Jef Denyn, founder of the Mechelen school. He has played in concerts throughout Europe and the US (where carillon-playing is highly regarded) and is also visiting professor at the State University of Saint-Petersburg and the Dutch Carillon Institute in Dordrecht.

The Mechelen Carillon School is renowned worldwide and attracts 60 students a year from 12 different countries. The town boasts four carillons, including one used by students.