"Song Sung Blue" is a 1972 hit song written and recorded by Neil Diamond, inspired by the second movement of Mozart's Piano Concerto #21. It was released on Diamond's album Moods, and later appeared on many of Diamond's live and compilation albums. The song was a #1 hit on the Billboard Hot 100 chart in the United States for one week, the week of July 1, and it spent twelve weeks in the Top 40. It also reached #14 on the UK Singles Chart.

The Piano Concerto No. 21 in C major, K. 467, was completed on 9 March 1785 by Wolfgang Amadeus Mozart, four weeks after the completion of the previous D minor concerto, K. 466.