Doctor Rhythm (1938)

Dr. Bill Remsen (Bing Crosby), a fashionable New York singing physician , poses as a policeman to save to save his best friend's job Officer Lawrence O'Roon (Andy Devine). He quickly finds out that a policeman's lot is not a happy one when he finds his assignment is to serve as the personal bodyguard of the quirky socialite Mrs. Lorelei Dodge-Blodgett (Beatrice Lilliie). But duty blends pleasantly with love when Mrs. Dodge-Blodgett orders him to guard Judy Marlowe (Mary Carlisle), her pretty niece who wants to runaway with a gangster. But music has charm , even for a spoiled rich girl, and after a few inoculations of Dr. Remsen's crooning, Judy decides to engage her bodyguard on a lifetime contract.