"In a Sentimental Mood" is a jazz composition by Duke Ellington that is also performed as a song. Ellington composed the piece in 1935 and recorded it with his orchestra the same year. Lyrics were later written for the tune by Manny Kurtz; as was the custom of the day, Ellington's manager Irving Mills — who never wrote a note of music or a word of lyrics in his life — cut himself in for a percentage of the publishing, the song credited to all three.
According to Ellington, the song was born in Durham, North Carolina. "We had played a big dance in a tobacco warehouse, and afterwards a friend of mine, an executive in the North Carolina Mutual Insurance Company, threw a party for Amy. I was playing piano when another one of our friends had some trouble with two chicks. To pacify them, I composed this there and then, with one chick standing on each side of the piano." The original recording featured solos by Otto Hardwicke, Harry Carney, Lawrence Brown, and Rex Stewart.
"In a Sentimental Mood" makes use of a musical technique called contrapuntal or chromatic embellishment of static harmony. This is also sometimes referred to as a line cliché.
Ellington recorded his best-known version together with John Coltrane, which is featured on Duke Ellington and John Coltrane (1963) and Coltrane for Lovers (2001). The original was recorded in F major, starting on D minor, but the later Ellington and Coltrane version was performed in the key of D-flat major, mainly from B-flat minor 7th to E-flat minor 7th, and then A-flat 13th to D-flat major 7th, with an interesting interlude in A major.