Beginning in  1995, he has been a permanent member of the group "German Brass". Beginning in 1997,   Köller taught as a visiting professor to the University of Music and Dramatic Arts in Graz.
Starting in 1995, he became a consistent member of the musical ensemble "German Brass".  From 1997 onward, he began teaching as a guest professor at the University of Music and Dramatic Arts in Graz.