Not long ago I was judging the Met Auditions in Chicago when some of the local sponsors asked me how I could tell what I liked and didn’t like. This inspired me to draw up a list of relatively objective vocal qualities one could listen for. Some are more objective than others, and all do demand some close attention paid.

1. Range. Does the voice have a large consistent range – close to three octaves for women and two and a half for men, with no breaks or audible transitions from one kind of sound to another?
2. Over this range, are there consistent vowels formed, so that the <a> or <i>, for example remain the same, rhymed, you might say, throughout the range.
3. Over this range, is the vibrato pulse consistent? No wobble, for example on the top.
4. Speaking of vibrato, are there 5 to 7 iterations per second, with either no interference with the perception of the pitch, or an interruption of the sound? The first is termed a wobble, the second, a bleat. The most subjective or mysterious aspect of vibrato is a liveliness or spin, like Bjoerling’s, for example.
5. Pitch. Does the singer sing in tune? If not, a technical flaw is revealed. In my experience this is more likely than simply bad hearing on the part of the singer.
6. Legato. Does the voice move from pitch to pitch without noticeable bumps, unless the singer is foolishly accenting unnecessarily, generally a bad idea.
7. Can the voice move quickly in fioritura passages, can words be articulated in recitative?
8. Diction. Some diction issues, like perceptible vowels and audible consonants, are technique issues. But beyond articulation and audibility lies the most important challenge of diction: conveying a thought. This last is difficult to teach because it is associated with musicality, the rarest of musical gifts. Can we help a young singer to phrase in a way that responds to the shape and music of a phrase? Sometimes…..
9. Mesa di voce. Can a voice on any pitch or vowel move from piano to forte and back again with no breaks or interruptions or vowel shifts?
10. Physical symptoms. Is the singer’s body perceptibly tense? This kind of tension can be seen as part of the act of singing rather than the act of acting. Does the singer’s mouth shape itself in odd and distracting ways?

For us singers and voice teachers, each of these categories can be regarded as challenges, goals to move closer to. Musicality is sometimes revealed as a voice learns to operate less arduously and more freely. And sometimes a singer can be inspired by listening to great singing, not in order to imitate the voice (each voice is unique) but to become aware of the great range of choices that every phrase offers.