An investigation to determine the significance of formant frequencies, pitch, and source‐spectrum slope on voice classification is reported. Eight professional singers sang five common vowels on four common pitches, and, in a forced‐choice test, vocal pedagogues classified the vocalization as tenor, baritone, or bass. Formant frequency and pitch differences accounted for most of the jury‐ evaluation results. To evaluate more accurately the significance of formant frequencies, pitch, and voicing and source‐spectral slope on voice classification, vowel synthesis was employed. Measurements of spoken vowel vocalizations revealed higher formant frequencies in tenor timbre type and lower formant frequencies in bass timbre type. Long‐time‐average spectra seem to afford a good estimate of voice classification. Formant‐frequency percentage differences between basses and tenors were similar to those found between males and females, suggesting that the mouth and pharynx lengths, known to differentiate females and males, probably also differentiate tenors and basses.