Lt. Gruber's piano playing is often Played for Laughs as he serenades a deeply uncomfortable René, but almost his entire repertoire is politically dangerous for a man living under Nazi rule:
"Can't Help Lovin' That Man" was written by two American Jews
"The Boys in the Back Room" and "Falling In Love Again" were originally performed by Marlene Dietrich
"He's Funny That Way" was popularised by African-American Billie Holiday
"Mad About the Boy" was written by semi-openly homosexual Noël Coward, who was scheduled for arrest and execution should the Nazis have invaded Britain. Couple all this with Gruber's own homosexuality and the fact that he doesn't bat an eyelid when he mistakes René's "father" (actually René in disguise) for a rabbi, and he may very well be using his music to telegraph his feelings about the regime.
