Correlates of the belt voice: a broader examination.

The purpose of the present study was to further clarify a definition of belting in physiological and acoustic terms. Twenty professional female singers produced triads ascending by halftone steps from C₄ to C₅ and sang the last four measures of a popular Broadway ballad in both legit and belt styles. Vocal source differences between belt and legit singing modes were assessed with respect to closed quotient (CQ) and speed quotient (SQ) computed from the electroglottographic waveform during productions of /ma/ triads covering approximately one octave. Differences in supraglottal configuration were evaluated in terms of the ratio (dB) of the amplitudes of the first and second harmonics of /I/ sustained at the pitch A₅(b), as noted in the long-term average spectrum. CQ did not vary significantly as a function of the singing type. SQ, however, decreased monotonically in association with increasing pitch level in both legit and belt singing styles. Belt mode phonations had higher SQ's than those of legit mode phonations at the same pitch. A repeated-measures analysis of variance demonstrated that the data differences associated with both pitch level and with singing mode were significant beyond P < 0.01. Analysis of the relative magnitude of the first and second harmonics showed that the direction of the harmonic ratio varied between styles. In legit singing style, H₁ was always stronger than H₂, but this unidirectionality of amplitude was not characteristic of belt singing, for which the second harmonic had greater amplitude in 25% of the cases. Implications of these results are discussed with regard to a new definition of belting.