"I Let a Song Go Out of My Heart" is a 1938 composition by Duke Ellington, with lyrics added by Irving Mills, Henry Nemo and John Redmond. The song became a number one hit for Ellington in 1938, and vocal versions by Benny Goodman (with Martha Tilton singing) and Mildred Bailey soon followed. Dinah Washington recorded the song in her album After Hours with Miss "D" in 1954, and Thelonious Monk covered it in 1955 on his album Thelonious Monk Plays the Music of Duke Ellington.