Ab Koster studied horn at the Royal Conservatoire and concluded his studies with the Prix d'Excellence. He continued his studies at the Folkwang-Hochschule in Essen (Germany) with Hermann Baumann. From 1977 to 1990 Ab Koster was first hornist of the NDR Symphony Orchestra in Hamburg. In 1990 he left the orchestra to concentrate on a career as soloist.
He performed with numerous orchestras and worked with many conductors, such as Frans Brüggen, Nikolaus Harnoncourt, Ton Koopman, Bernhard Klee, Krzystof Penderecki and Günther Wand. Ab koster plays both the modern horn as well as the historic natural horn. He has an exceptional international reputation thanks to his colaborations and CD recordings with many famous musicians.
 
The focus of the masterclass in on classical and neoclassical music as well as natural horn. Beethoven, Mozart and Hindemith are part of the repertoire.