After many years of working as an assistant to other artists he has decided to work as composer and arranger on his own account. Since that decision Karel has written several classical pieces for symphonic orchestra ( Flemish Radio Orchestra ) , pianosolo, organ ( International Organ festival Veurne ), a brass quintet (for soloists of the Belgian National Orchestra) as well as a string quartet for soloists from the Luxembourg Philharmonic Orchestra, and also performed by the Rubio String Quartet ), a piece for violin and piano.

His composition "Changes" won the BAP-Sabam price (09/2000) for the European Jazz Contest in Hoeilaart.
His composition "Senses for life" won the Sabam contest (08/2005) for Belgian jazz themes and will be the imposed piece for all the finalists of Jazz Hoeilaart 2005.

Van Marcke's work will soon be international published, but details can't be revealed yet.

Van Marcke is composing pieces for his new septet "Chroma" and is also working on a large piece for choir with jazz singer and trio for the Festival van Vlaanderen. (11/2007)

He released already 2 recordings and toured through Belgium with his 13 piece band 'JAMBANGLE'. The band has always included top Belgian jazz musicians.

He has been working with Frank Vaganée, Erwin Vann, Laurent Blondiau, Bart Quartier, Herman Pardon, Nicolas Kummert, Marc Godfroid, Bart Defoort, Fabrice Alleman, Teun Verbruggen, Tom Van Landuyt, regisseur Alain Pringels, Michel Bisceglia, Dieter Limbourg, ea.