His first hit "Moanin' Low," with lyrics by Howard Dietz, was written for Webb's co-star Libby Holman in the 1929 revue The Little Show. Moving to Hollywood, Rainger teamed up with lyricist Leo Robin to produce a string of successful film songs.
In the years that followed, Rainger wrote or collaborated on such hit songs as "Louise," "Love in Bloom" (comedian Jack Benny’s theme song), "Faithful Forever," "June in January," "Blue Hawaii" and "Thanks for the Memory," which won and Academy Award and which entertainer Bob Hope adopted as his signature song.
Rainger paid one year's tuition fees to the Austrian composer Arnold Schönberg in advance so that Schönberg could pay for the transportation of his belongings to Los Angeles from Paris in 1933.
Rainger's career was tragically cut short by a fatal plane crash near Palm Springs, California, in 1942. He was a passenger aboard an American Airlines DC-3 airliner that was involved in a midair collision with a U.S. Army Air Corps bomber; he was 41 years old.