Modeling source-filter interaction in belting and high-pitched operatic male singing.

Nonlinear source-filter theory is applied to explain some acoustic differences between two contrasting male singing productions at high pitches: operatic style versus jazz belt or theater belt. Several stylized vocal tract shapes (caricatures) are discussed that form the bases of these styles. It is hypothesized that operatic singing uses vowels that are modified toward an inverted megaphone mouth shape for transitioning into the high-pitch range. This allows all the harmonics except the fundamental to be "lifted" over the first formant. Belting, on the other hand, uses vowels that are consistently modified toward the megaphone (trumpet-like) mouth shape. Both the fundamental and the second harmonic are then kept below the first formant. The vocal tract shapes provide collective reinforcement to multiple harmonics in the form of inertive supraglottal reactance and compliant subglottal reactance. Examples of lip openings from four well-known artists are used to infer vocal tract area functions and the corresponding reactances.