Vowel-pitch matching in Wagner’s operas: Implications for intelligibility and ease of singing

European vowels are mainly distinguished by the two lowest resonance frequencies (R1 and R2) of the vocal tract. Once the pitch frequency f(0) exceeds the value of R1 in normal speech, sopranos can deliberately "tune" R1 to match f(0). This increases loudness, uniformity of tone, and ease of singing, at some cost to intelligibility. Resonance tuning would be assisted if the pitch of the note written for a vowel corresponded with its usual range of R1. Analysis of several soprano roles indicates that Wagner aided the acoustics of the soprano voice at high pitch when setting text to music.