Koen Cosaert is director of the Royal Carillon School Jef Denyn in Mechelen, the eldest and most famous institute for carillon art in the world. As part of the Belgian carillon culture the school has the recognition of UNESCO as 'best safeguarding practice' for the intangible cultural heritage. Koen Cosaert has been teaching since 1987 campanology and carillon performance.
He is carillonneur of the Belgian cities of Kortrijk, Roeselare, Harelbeke and Izegem. As performer he has toured Europe, The United States, Canada, Australia and Japan.
Currently he is vice-president of the Flemish Carillon Association (VBV). From 2011 until 2017 he has been secretary of the World Carillon Federation.