A waltz, probably deriving from German Ländler, is dance music in triple meter, often written in 34 time. A waltz typically sounds one chord per measure, and the accompaniment style particularly associated with the waltz is to play the root of the chord on the first beat, the upper notes on the second and third beats.

"The Blue Danube" is the common English title of "An der schönen blauen Donau", Op. 314, a waltz by the Austrian composer Johann Strauss II, composed in 1866. Originally performed on 15 February 1867 at a concert of the Wiener Männergesang-Verein, it has been one of the most consistently popular pieces of music in the classical repertoire. Its initial performance was considered only a mild success, however, and Strauss is reputed to have said, "The devil take the waltz, my only regret is for the coda—I wish that had been a success!"