Vocal tract resonances in singing: Strategies used by sopranos, altos, tenors, and baritones

The first two vocal tract resonances ( R 1 and R 2) of 22 classically trained sopranos, altos, tenors, and baritones were measured while they sang four different vowels over their normal pitch range. The resonances of the tract and the harmonics of the voice were measured simultaneously by injecting a broadband acoustic current into the tract at their mouth. Sopranos were found to tune R 1 close to the fundamental frequency f 0 ( R 1: f 0 tuning) over at least part of their upper range for all vowels studied, particularly when f 0 was around or above the value of R 1 for speech. Additionally, most sopranos employed R 2:2 f 0 tuning over some of their range, often simultaneously with R 1: f 0 tuning. Altos used R 1: f 0 tuning for vowels having lower values of R 1 in speech, but can switch to R 1:2 f 0 tuning in the lower part of their range. Tenors and baritones generally used R 1:2 f 0 and R 1:3 f 0 tunings over part of their range and employed a number of different tunings to higher harmonics at lower pitch. These results indicate that singers can repeatedly tune their resonances with precision, and that there can be considerable differences in the resonance strategies used by individual singers, particularly for voices in the lower ranges.