 Due to a labor dispute, the principal actors had to "live" on the  set for a few weeks to avoid crossing picket lines.  Marlene Dietrich (qv) took the time to learn how to play the  zither; it was said she drove the rest of the cast and crew mad with  her attempts to perfect her technique. Her efforts paid off,  however, as illustrated in the scene where she plays the zither very  competently.