Vibrato
Click on the word in question and Wikipedia will take you down the middle road of controversy sliding off the pavement a little here and there to the side belonging to the mechanical school.
The vibrato belongs to the human voice and should not be spun as a symptom. It belongs to the character of each voice. The lack of “spontaneous” vibrato is a symptom. I call losing the vibrato the first symptom of vocal stress, and getting it back and settled the confirmation that stress has been alleviated.
