Resonance Strategies in the Upper Range of Western Operatic Tenors

High notes pose a challenge for classical tenors due to physiological and acoustic aspects. According to nonlinear source-filter interactions, it is beneficial in these notes to position the resonances just above the frequency of their closest harmonics, amplifying them while avoiding phonatory discontinuities. Intentional tuning of resonances to harmonics in the high tenor tessitura has been described in the literature.

Identify the resonance strategies employed by operatic tenors in high notes.

Five professional tenors were recorded emitting the vowels /a, e, i, o, u/, sung in ascending scales between the notes C3 (131 Hz) and C5 (523 Hz) and spoken in carrier sentences. The frequencies of the first two resonances were extracted through inverse filtering, as well as the amplitudes of the first four harmonics and the peak in the singer's formant region in the radiated spectrum.

From low to high notes, the frequencies of the first two resonances of all vowels tended to converge. Resonance tuning was most employed in the passaggio (first resonance tuned to the second harmonic, second resonance to the fourth harmonic) and at its upper limit (second resonance tuned to the third harmonic). In the highest notes, the balanced distribution of energy among the lower harmonics was more frequent, with the more dramatic voices exhibiting an equally strong singer's formant. Only in the vowel /i/ did first resonance tunings to the first harmonic occur.

The vowels became progressively less distinguishable towards the high notes. Systematic resonance tuning was not observed in the high notes, with a greater occurrence of similarly strong lower harmonics, without strong distinct spectrum envelope peaks. Where resonance tuning was identified, there was no apparent preference for positioning the resonances above or below the frequency of their closest harmonics.