MUSIC

Karan Armstrong, prima donna of the Deutsche Oper in West Berlin--where her husband, Gotz Friedrich, is general director--will sing her first Leonore in “Fidelio” when the Music Center Opera stages Beethoven’s opera in 1990. None less than Placido Domingo will play her on-stage husband, Florestan. The former Los Angeles soprano is scheduled to return here the following year to play the Marschallin in a new production of Richard Strauss’ “Der Rosenkavalier.”