Born Ralph Reichenthal in New York City, United States,[1] Rainger initially embarked on a legal career, having obtained his law degree at Brown University in 1926.

[3] These were as soloist, accompanist to singers, and as duo-pianist with Adam Carroll or "Edgar Fairchild" (the name Milton Suskind used for commercial work).

His first hit "Moanin' Low", with lyrics by Howard Dietz, was written for Clifton Webb's co-star Libby Holman in the 1929 revue The Little Show.

[1] He teamed up with lyricist Leo Robin to produce a string of successful film songs,[9] including "I'll Take An Option On You",[1] from the Broadway hit show Tattle Tales (1933).

In the initial 1942 press coverage of the crash, the collision was not acknowledged; Betty Rainger later sued American Airlines and won a substantial judgement late in 1943.