Adjective
multiphonic (not comparable)
(music) Having the character of multiphonics: sounding two or more pitches at the same time
String instruments String instruments can also produce multiphonic tones when strings are divided in two pieces. Source: Internet
The most developed instrument for playing multiphonic tones is the Sitar in which there are sympathetic strings which help to bring out the overtones while one is playing. Source: Internet