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.
From 1995 onwards, he has been a permanent member of the group "German Brass". From 1997 onwards, Köller taught as a visiting professor at the University of Music and Dramatic Arts in Graz.