What makes judges love a classical singer’s voice? A study from Keio University in Japan suggests it comes down to vibrato, resonance, expressiveness, and a particular “ring” in the voice. Singing louder and hitting every note in tune made less difference to the scores than you might expect.
Voice competitions usually give singers a single overall score, and the criteria are rarely spelled out. Teachers and judges often describe voices in vague terms like “warm,” “ringing” or “focused.” The researchers wanted to pin down what experts are actually responding to.
A mock competition
The team staged a simulated competition in a concert hall. Twenty-two classical singers, 10 men and 12 women, each sang the same Italian art song, “Caro mio ben,” without accompaniment. Five expert judges gave each performance an overall score out of 100 and rated six qualities: vibrato, resonance, timbre, diction, intonation and expressiveness. The researchers also measured acoustic features of each voice.
The study was led by Haruka Kondo, an operatic soprano and doctoral student in vocal science, with Sotaro Kondoh and Shinya Fujii of Keio’s Research Center for Music Science.
What scored well
Singers rated higher for vibrato, resonance and expressiveness got higher overall scores. Timbre, diction and intonation showed no clear link to the overall score.
Acoustically, voices with more energy in the 2 to 4 kilohertz range scored higher for both men and women. That range is associated with the “singer’s formant,” which gives trained classical voices a bright, ringing quality that carries over an orchestra without a microphone. Sheer loudness wasn’t linked to higher scores.
Judges also seemed to treat vibrato differently by gender. Men with faster vibrato got lower scores, while women with wider vibrato got higher ones.
“Our results show that something as personal and artistic as ‘a beautiful voice’ can be partly understood through science,” Kondo said. She said the measurements could help students understand instructions like “let it ring more,” make competition scoring clearer, and improve singing-training apps.
Limitations
The study involved one song, 22 singers and five judges in a single simulated competition, so the results may not hold across other repertoire, larger competitions or judges from other traditions.
Source: Kondo, H., Kondoh, S., & Fujii, S., “Vocal Evaluation of Classical Singing in a Concert Hall: Perceptual and Acoustic Associations with Overall Scores in Male and Female Singers,” Journal of Voice, 2026. doi:10.1016/j.jvoice.2026.09.070; Keio University news release, Nov. 4, 2026.
