Complex sentence: From 1988 to 1991, Schirmer was Generalmusikdirektor (GMD) of the city of Wiesbaden, serving also as artistic director of symphonic concerts at the Hessisches Staatstheater Wiesbaden.
Split into simpler sentences: From 1988 to 1991, Schirmer was "Generalmusikdirector" (GMD) of the city of Wiesbaden. He has also served as artistic director of symphonic concerts at the Hessisches Staatstheater Wiesbaden.