Multiphonics is an extended technique in instrumental music in which a monophonic instrument (one which generally produces only one note at a time) is made to produce several notes at once.

Multiphonics in wind music are primarily a 20th century technique, first explicitly called for in the Sequenza for solo flute by Luciano Berio and Proporzioni for solo flute by Franco Evangelisti, 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.

On woodwind instruments - for example saxophone, clarinet, oboe and flute - multiphonics can be produced either with new fingerings, by using different embouchures, or voicing the throat with conventional fingerings. There have been numerous fingering guides published for the woodwind player to achieve harmonics. Multiphonics on reed instruments can also be produced in the manners described below for brass instruments.