There was no notable creation of music in the Hitler era in Germany, although artists and composers like Van Karajan, Fuertwaengler, Wagner and Schwarzkopf were treated as heros of the Reich. Many composers and conductors like Bruno Walter, Georg Solti, Mahler, Korngold, and Otto Klemperer fled the country or lost their positions with German and Austrian orchestras.
The greatest Russian composers of the Soviet era were Prokoviev, Shostakovich, Stravinsky and Rachmaninoff. The latter two fled the country. Prokoviev spent many years in the USA but returned during WW2. Those who remained had to try to please Comrade Stalin, or risk imprisonment. Somehow the Russians continued to produce great music, and ballet, in the totalitarian era.
Thise are my opinions. You should do your own listening and research and form you own.