extended technique
Any method of sound production on an instrument that goes beyond its standard playing technique
In Depth
Extended techniques vastly expand the sonic palette of traditional instruments. Examples include string techniques (col legno, sul ponticello, Bartók pizzicato), wind techniques (multiphonics, circular breathing, key clicks, singing while playing), piano techniques (preparation, string plucking, harmonics), and vocal techniques (Sprechstimme, throat singing, tongue clicks). These techniques became systematised in the 20th century, and most contemporary compositions require at least some extended techniques from their performers.
Helmut Lachenmann built an entire compositional aesthetic around extended techniques, which he called musique concrète instrumentale — using instruments to produce noise-based sounds.