Excessive vibrato has spoiled many good voices.
"Resonance in Singing and Speaking"
Thomas Fillebrown
This ebbing and flowing undulating wave of sound upon sustained notes was the source from which sprung the modern tremolo and vibrato, which is so much in evidence among singers and so offensive to all really refined musical taste.
"Sixty Years of California Song"
Margaret Blake-Alverson
There seems to be considerable confusion among singers and even writers as to the use and meaning of tremolo and vibrato.
"Sixty Years of California Song"
Margaret Blake-Alverson