Multiphonic

A multiphonic is an extended technique on a monophonic musical instrument (one that generally produces only one note at a time) in which several notes are produced at once. This includes wind, reed, and brass instruments, as well as the human voice. Multiphonic-like sounds on string instruments, both bowed and hammered, have also been called multiphonics, for lack of better terminology and scarcity of research.

Multiphonics on wind instruments are primarily a 20th-century technique, though the brass technique of singing while playing has been known since the 18th century and used by composers such as Carl Maria von Weber. Commonly, no more than four notes will be produced at once, though for some chords on some instruments it is possible to get several more.