Walter Hamor Piston, Jr. (January 20, 1894 – November 12, 1976), was an American composerof classical music, music theorist, and professor of music at Harvard University.

He taught at Harvard from 1926 until his retirement in 1960. His students include Samuel Adler, Leroy Anderson, Arthur Berger, Leonard Bernstein, Gordon Binkerd, Elliott Carter, John Davison, Irving Fine, John Harbison, Karl Kohn, Ellis B. Kohs, Gail Kubik, Billy Jim Layton, Noël Lee, Robert Middleton, Robert Moevs, Daniel Pinkham, Mildred Barnes Royse, Frederic Rzewski, Allen Sapp, Harold Shapero, and Claudio Spies, as well as Frank D’Accone, Ann Ronell, Robert Strassburg, Yehudi Wyner, and William P. Perry. See: List of music students by teacher: N to Q#Walter Piston.

In 1936, the Columbia Broadcasting System commissioned six American composers (Aaron Copland, Louis Gruenberg, Howard Hanson, Roy Harris, William Grant Still and Piston) to write works for broadcast on CBS radio. Piston wrote his Symphony No. 1and conducted its premiere with the Boston Symphony Orchestra on April 8, 1938.

Piston’s only dance work, The Incredible Flutist, was written for the Boston Pops Orchestra, which premiered it with Arthur Fiedlerconducting on May 30, 1938. The dancers were Hans Weiner and his company. Soon after, Piston arranged a concert suite including “a selection of the best parts of the ballet.” This version was premiered by Fritz Reiner and the Pittsburgh Symphony Orchestra on November 22, 1940. Leonard Slatkin and the St. Louis Symphony Orchestra included the suite in a 1991 RCA Victor CD recording that also featured Piston’s Three New England Sketches and Symphony No. 6.

Piston studied the twelve-tone technique of Arnold Schoenberg and wrote works using aspects of it as early as the Sonata for Flute and Piano (1930) and the First Symphony (1937). His first fully twelve-tone work was the Chromatic Study on the Name of Bach for organ (1940), which nonetheless retains a vague feeling of key. Although he employed twelve-tone elements sporadically throughout his career, these become much more pervasive in the Eighth Symphony (1965) and many of the works following it: the Variations for Cello and Orchestra (1966), Clarinet Concerto (1967), Ricercare for Orchestra, Fantasy for Violin and Orchestra (1970), and Flute Concerto (1971).

In 1943, the Alice M. Ditson Fund of Columbia University commissioned Piston’s Symphony No. 2, which was premiered by the National Symphony Orchestra on March 5, 1944 and was awarded a prize by the New York Music Critics’ Circle. His next symphony, the Third, earned a Pulitzer Prize, as did his Symphony No. 7. His Viola Concerto and String Quartet No. 5 also later received Critics’ Circle awards.