Rarely have I heard a singing teacher say to a student, you are making too much sound, if the sound itself was pleasing and the student seemed comfortable. That is because the sound alone was the criteria, not the functionality of the sound. Not good.
If a student sounds “nice” or “good” and seems relatively comfortable, but is having “trouble” with high notes, or with singing softly, or with vibrato, or “support”, and that student has a good voice, is musical and is clearly motivated to study, practice and has made progress in the past, something is wrong.
The student has not “forgotten” how to sing correctly. She has not forgotten how to support. She has not “lost” her sense of making her voice do what she would like it to.
She has, instead, developed technical problems which are usually the result of singing too loudly for too long. While someone with a lovely instrument can absolutely learn to sing in a full, round and relatively loud manner, particularly on high notes, being able to do this effectively and being able to continue to do this in a role, in a series of performances, over an orchestra, might be wearing and ultimately, the vocal mechanism will begin to collapse in on itself. Hardly anyone realizes this, although some considerable amount of lip service is paid to not having young singers do repertoire that is not “too big” for them.
A healthy young person might be able to generate a loud sound (high SPL or decibel level) and the vocal folds might be able to take the requisite breath pressure blasting away from the force of the belly’s contraction, but the muscles of the tongue, the throat (including the constrictors) and the back of the mouth might be less likely to continue to behave comfortably. Constriction, resulting from too much effort in the wrong places, can begin to creep in and cause first musical and then physical problems.
If the teacher doesn’t understand this, and many do not, they will tell the student “you are forgetting how to properly support the tone” or “you are not keeping the tone up high in the masque” or “you are not opening enough to spin the sound” or “you are distorting the vowel” and the poor student has nothing to say in her own defense because, as far as she can tell, she’s just doing the best she can to sing and express the music. Maybe, who knows, all these things she is accused of being/doing are accurate and maybe she is just unconscious about them. Maybe, too, this inability to know if you know is cause to doubt yourself and go along with whatever it is that you are told.
If, however, the student is not told anything about what she is or is not doing and is instead asked, “what are you doing” and “how does that feel” as if it mattered, and if the student is guided to actually take some of the effort of the vocal production out until the sound feels easier and freer, maybe she will realize on her own that what is wrong is not so much how she wants to sing but how she is capable of singing. There is a big difference.