This ignoring of the psychological nature of the impressions of tone is not necessarily detrimental to successful instruction. On the contrary, the master's empirical insight into the vocal operations of the pupil would probably not be advanced by an understanding of the psychological process. It is sufficient for the teacher's purpose to hear that the pupil's voice is caught in the throat. What robs this hearing, or feeling, of all value is this: the master attempts to interpret the sensation as an indication of the need of some specific muscular action, to be directly performed by the pupil. To this end he cites the mechanical rule, assumed to be indicated by the pupil's faulty vocal action. This may be, for example, the opening of the throat to give room for the tone to expand. It seems so perfectly simple to the teacher;--the pupil narrows his throat, and so holds in the tone; let him expand his throat and the tone will come out freely. This conclusion seems so clearly indicated by the sound of the tones that the master almost inevitably gives the precise instruction: "Open your throat and let your voice come out." This sums up, to the master's satisfaction, everything the pupil need do to correct this particular fault of tone-production. Other sets of sympathetic sensations, awakened by badly produced tones, are interpreted in the same manner. A tone heard to be held in the back of the throat is believed to indicate the need of bringing the voice forward in the mouth. Other forms of throaty production are taken to show a lack of support, a wrong management of the breath, a need of breath-control, a misuse of nasal resonance, or an improper action of the vocal cords. In all these attempts to interpret sympathetic sensations by means of mechanical doctrines the teacher naturally relies on those doctrines in which he believes most firmly. Sympathetic sensations are indeed sometimes cited in proof of certain theories of breath-control, and also of nasal resonance. Both these topics are worthy of separate attention. _Sympathetic Sensations and Nasal Resonance_ One of the most widely accepted theories of the vocal action is that the higher notes of the voice are influenced by reinforcing vibrations located in the nose and forehead. Whether this idea was derived more from direct than from sympathetic sensations need not be determined now. It is at any rate certain that a perfectly sung tone gives to the hearer the impression of nasal influence of some kind. The exact nature of this influence has never been determined. It may be air resonance, or sounding-board resonance, or both combined. Satisfactory proof on this point is lacking. In the belief of the practical teacher, however, this impression of nasal influence is the strongest argument in favor of nasal resonance.