Rudersdorff had begun to recognize the effect of nasal resonance, but she left no published record of her conclusions.

It does not appear that she or her contemporaries realized the true value of the nasal and head cavities as reinforcing agents in the production of tone, or appreciated their influence upon its quality and power.
There are perhaps few subjects on which a greater variety of opinion exists than on that of voice culture, and few upon which so many volumes have been written.

Few points are uncontested, and exactly opposite statements are made in regard to each.
Formerly great stress was laid upon the distinction between "head tones" and "chest tones," "closed tones" and "open tones." The whole musical world was in bondage to "registers of the voice," and the one great task confronting the singer and vocal teacher was to "blend the registers," a feat still baffling the efforts of many instructors.
Many teachers and singers have now reached what they consider a demonstrated conclusion that registers are not a natural feature of the voice; yet a large contingent still adhere to the doctrine of "register," depending for their justification upon the unreliable evidence furnished by the laryngoscope, not realizing that there will be found in the little lens as many different conditions as the observers have eyes to see.

Garcia himself, the inventor of the laryngoscope, soon modified his first claims as to its value in vocal culture.
On this point we have the testimony of his biographer, M.S.

McKinley: "As far as Garcia was concerned, the laryngoscope ceased to be of any special use as soon as his first investigations were concluded.