In the autumn of 1948 , Fischer-Dieskau became principal lyric baritone at the StÃ dtische Oper Berlin ( Municipal Opera , West Berlin ) , making his first opera performance in the role of Posa in Verdi 's Don Carlos under the conductor Ferenc Fricsay . In the autumn of 1948 , Fischer-Dieskau was engaged as principal lyric baritone at the StÃ dtische Oper Berlin ( Municipal Opera , West Berlin ) , making his debut as Posa in Verdi 's Don Carlos under Ferenc Fricsay .