When the two come to compare notes at the end of the performance the trained critic will be utterly unable to convey to his friend his impressions of the player's technique. Vividly clear as it is to the critic, his understanding of tonal values is lodged solely in his cultivated ear. This understanding cannot be imparted in words; it must be acquired by experience in actual listening to music.

Let us now imagine this same critic to be listening to a singer, not an artist of the first rank, but one whose voice is marred by some slight faults of production. In this case the critic will note exactly the same sort of differences in tonal value as in the case of the violinist. Some of the singer's notes will be perfect musical tones, others will be marred by faults of intonation or of quality. But a great difference will be noted between faulty tones played on the violin, and faulty tones sung by the human voice. In addition to their blemishes as musical tones, the faulty notes of the voice also convey to the critical listener an idea of the state of the singer's throat in producing them.

Every blemish on the beauty of a vocal tone, every fine shade of quality which detracts from its perfection, indicates to the critical hearer some faulty action of the singer's vocal organs. The more faulty the musical character of the singer's tones the more pronounced is this impression of faulty production. On the other hand, just so nearly as the singer's tones approach perfection as musical sounds, so do they also impress the ear of the critical listener as indicating the approach to the perfect vocal action.

The critic could not impart to his untrained friend the impressions made by the violinist's tones. Somewhat the same is true of the impressions made by the tones of the voice on the critical ear. In voices of extremely nasal or throaty sound these blemishes can, of course, be detected by the ordinary hearer. But the fine shades of difference in vocal tone quality, heard by the trained critic, cannot be noted by the inexperienced listener.

This fine ability to discriminate between musical sounds comes only through experience in listening to music, better still, when this has been combined with the actual study of music. But the ability to judge the vocal actions of singers, through the sympathetic sensations of tone, does not depend on any actual exercise of the listener's own voice. For the developing of this ability the exercise of the ear suffices. The mere exercise of the ear, in listening to singers, entails also the training of what may be called the "mental voice." Attentive listening to voices, involving as a natural consequence the sub-conscious impressions of sympathetic sensations, results in the development of a faculty to which this name, the mental voice, very aptly applies.

A music-lover whose experience of hearing singing and instrumental music has been wide enough to develop the mental voice in a fair degree, possesses in this faculty a valuable means for judging singers. The mental voice carries on a running commentary on the manner of production of all the voices to which this music-lover listens. At every instant he is informed of the exact condition of the singer's throat. For him there is an almost infinite variety of throaty tones, each one indicating some degree and form of throat tension or stiffening. A perfect vocal tone, on the other hand, is felt to be perfectly produced, as well as heard to be musically perfect.

Equipped with a highly trained sense of hearing, and the resulting faculty of mental voice, the lover of singing has an unfailing insight into the operations of the vocal mechanism. This understanding of the workings of the vocal organs is the empirical knowledge of the voice.

This empirical knowledge of the voice can be possessed only by one who is equipped with a highly cultivated ear. The keener the ear the more precise and definite is this understanding of the voice. Season after season, as the music-lover continues to attend concerts, operas, and recitals, his feeling for the voice becomes gradually more keen and discerning.

Further, empirical knowledge of the voice can be acquired in no other way than by actual experience in listening to voices. No matter how keen and definite are the impressions of throat action felt by the experienced hearer, these impressions cannot be described to the uninitiated. In fact, these impressions are to a great extent of a character not capable of being recorded in precise terms. The general nature of a throaty tone, for example, is thoroughly understood. But of the thousands of varieties of the throaty tone no adequate description can be given. Each observer must learn for himself to hear these fine shades of difference in tone quality.

Every experienced music lover has his own mental standard of tonal perfection. The trained ear knows how a perfect musical tone should sound, independent of the precise quality of the tone. The tone quality is determined, of course, by the instrument on which it is sounded. But along with the individual characteristics of the sound, the tones drawn from every instrument, to be available in the artistic performance of music, must conform to the correct standard. Knowing the general musical character of the tones of all instruments, the cultured hearer can at once detect any variation from this character. Further, he knows how the tones of a badly-played instrument would sound if the instrument were correctly handled. An unskilled trumpeter in an orchestra, for example, may draw from his instrument tones that are too brassy, blatant, or harsh. An observant hearer knows exactly what these tones would be if the instrument were skilfully played.