Louis Horst (born January 12, 1884 in Kansas City, Missouri, U.S.; died January 23, 1964 in New York City) was a choreographer, composer, and pianist. He helped to define the principles of modern dance choreographic technique, most notably the matching of choreography to pre-existing musical structure and the use of contemporary music for dance scores.
Horst was the musical director for the Denishawn company (1916 to 1925) before working as musical director and dance composition teacher for Martha Graham's school and dance company (1926 to 1948).
One memorable piece of advice that Horst gave dancers in his lessons in the 1930s, at times delivered in a sarcastic tone: "when in doubt, turn." This is a variant of Ted Shawn's famous line "When in doubt, twirl." The Grateful Dead Almanac adopted it as their motto.
Apart from being a personal friend and mentor to Graham, Horst worked and wrote scores for many other choreographers, including:
Horst composed scores for the Denishawn company, including Japanese Spear Dance (1919). He composed several of Graham's early group works: Primitive Mysteries (1931), Celebration (1934), Frontier (1935), and El Penitente (1940). For Anna Sokolow, Horst composed Noah (1935). He also composed several movie scores.
Horst taught art of choreography at Neighborhood Playhouse School of the Theater (1928-1964), Bennington College (1934-1945), Mills College, Connecticut College (1948–1963), Barnard College, Sarah Lawrence College, Columbia University, and The Juilliard School (1951-1964).