In addition, he is a member of the Long Beach Municipal Band and the Americus Brass Band, a Civil War period band. Other ensembles he has performed with include the Los Angeles Philharmonic, The New York Philharmonic, L.A. Chamber Orchestra, L.A. Opera, San Diego Symphony, Pacific Symphony, Opera Pacific and many other Southern California orchestras, theater orchestras, brass chamber ensembles, ballet and opera companies. He has also recorded soundtracks for many of the major studios in Hollywood.

Keen specializes on the alto, tenor bass and contra bass trombones, bass trumpet, euphonium and tuba