Rhythm on the River stars Bing Crosby and Mary Martin as star-crossed songwriters who step out from the shadows in the hopes of making it big. Oliver Courtney (Basil Rathbone) is a well-known composer of hit songs who is very much in demand. However, beneath the gloss of a well-polished performance lies the truth about Oliver's talent - it's the work of ghostwriters! Bob Summers (Crosby) writes the tunes and Cherry Lane (Martin) writes the lyrics - only neither knows the other exists and both believe they are collaborating with Oliver. When the two happen to meet, they discover they have a lot more in common than they ever imagined!