31 (1926–28) is an orchestral set of variations on a theme, composed by Arnold Schoenberg and is his first twelve-tone composition for a large ensemble.

Premiered in December 1928 by the Berlin Philharmonic conducted by Wilhelm Furtwängler, it was greeted by a tumultuous scandal.

Schoenberg opened a lecture on the composition with the following tyranny of the majority defense of less common aesthetics: "Far be it from me to question the rights of the majority.

But one thing is certain: somewhere there is a limit to the power of the majority; it occurs, in fact, wherever the essential step is one that cannot be taken by all and sundry.

"[6] The piece has been arranged for two pianos by Charles Wuorinen and this arrangement was set to a ballet, Schoenberg Variations (1996), by Richard Tanner of the New York City Ballet.