Multiphonics in Didjeridu Tones: Acoustical Effects of Applying the Tongue Positions of Spoken Vowels to a “Bilabial Aerophone.”

Without speaking or singing while they make sounds on a didjeridu, performers and pedagogues have applied the tongue positions they would otherwise use to produce vowels in speech or song and simultaneously “buzzing” their lips to produce the fundamental frequency of the instrument’s unchanging drone. By focusing on the sound pressures of particular frequencies within individual sonic spectra, we show how formants of specific spoken vowels are related to these added sounds, which might be termed “didjeridu formants.” Among our principal conclusions are the following. 1) At least four distinct sounds, rather than merely one or two, can be added, one at a time, to a didjeridu’s unchanging fundamental frequency. 2) Depending on the specific tongue positions that produce them, these added sounds are acoustically quite similar to each other with regard to their absolute frequencies and perceptually similar with regard to their contrasts between higher and lower “pitches.” 3) However, despite their similar absolute frequencies, these higher and lower pitches are assimilated to a particular instrument’s fundamental frequency. 4) Accordingly, in contrast to European-derived notions of “pitch,” these added sounds can be considered “timbral pitches,” or more precisely, “lingual pitches.”