One of the core principles of Italian bel canto is pronouncing vowels well, yet scientists and voice teachers have noted the lack of specific definition of vowel quality related to singing. This study analyzes vowels sung by Italian tenors of the 20th Century on Middle C in Italian operatic arias. The first and second formant frequencies of the vowels were measured and used to create a vowel chart specific to Middle C. The vowel chart reveals sixteen groupings which enable the definition of vowels specific to Middle C. The vowel groupings demonstrate patterns of formant tuning that align resonances of the vocal tract with the overtone series and display leveraging of nonlinear source-filter dynamics by the tenors. The findings provide specific information for singers who wish to tune their vowels for acoustic efficiency and aesthetics in the style of 20th century Italian opera singers. The findings also clarify various opinions and directives related to vowel quality encountered in the historic vocal pedagogy literature.
