In music, an nonet is a composition which requires nine musicians for performance. Unlike some other musical ensembles such as the string quartet, there is no established or standard set of instruments in a nonet. Composers of nonets often mix stringed instruments with winds, or woodwinds with brass, choosing the instruments so that each subgroup can form complete four-part harmony. For example, Franz Schubert's Eine kleine Trauermusik (1812) is for two clarinets, two bassoons, contrabassoon, two horns, and two trombones, while Louis Spohr's Nonet in F major (1813) is for flute, oboe, clarinet, bassoon, horn, violin, viola, cello, and double bass. Heitor Villa-Lobos and Bohuslav Martinu are among the twentieth-century composers who have written nonets.

see also Chamber music