He pops up in rock/free rock circles in '70s and joins bands like Jess and James, Musique Flexible and Aksak Maboul. He soon returns to his first love, jazz, and American organist Rhoda Scott invites him to join her on her European and African tours. He meets pianist Michel Herr, with whom he starts an intense collaboration, and becomes part of groups like Cosa Nostra (with Jack Van Poll), Casino Railway (with Philip Catherine), Solis Lacus, Camara Quintet, Abraxis, ...
In the late '70s he founds his own big band, called Act 12. Together, they record five albums between 1980 and 1996, with famous guest musicians such as Toots Thielemans, Joe Lovano, John Ruocco, ...
In 1982 he starts a new trio with John Ruocco and Jan-Louis Rassinfosse under the moniker The Trio.
Together with Nathalie Loriers, Erwin Vann, Jean-Louis Baudoin and Jean-François Prins he founds his own Felix Simtaine Quintet in 1989. In the '90s he is active with various bands, such as Eric Legnini's band (with Joe Lovano as fellow member).
He is often seen on the Belgian jazz scene, and has become a true pillar of Belgian jazz.