As phonation implies the use of the muscles (neuro-muscular mechanisms) of the (1) respiratory organs, (2) vocal bands, (3) resonance-chambers, and as these must all work in harmony, or be "co-ordinated," it will be seen that speaking and singing are physiologically highly complex. When, in addition, ideas and feelings are associated, and determine the exact form of these co-ordinations, the whole matter is seen to be still more complex. The emission of a single tone implies (1) an idea--the nature of the sound as to pitch and quality, (2) such an arrangement of all the parts of the mechanism as will produce it. The former involves memory of the tone; the latter, memories of former movements. Then, partly as a series of voluntary acts and partly reflexly, according as the student is more or less advanced, or the particular tone new or old in experience, do the various neuro-muscular arrangements pass into orderly action. In this process the ear is the chief guide, always in relation to memories. When one uses the printed page, the eyes also guide--_i.e._, the nervous impulses that pass in through these avenues determine the outgoing ones that bring the muscles into action. In doing so they rouse many others (associated nervous connections) which are highly important when an artistic result is to be reached. To consider a single case: Assume that the note [Illustration: a'] is to be sung. The following are required: (1) Memory of this tone. (2) Adaptation through eye and ear of all the neuro-muscular mechanisms required for (_a_) bringing the vocal bands into the correct position and degree of tension; (_b_) the proper shape, tension, etc., of the resonance-chambers; (_c_) that use of the breathing apparatus suitable to cause the proper vibrations of the vocal bands. All use of the voice implies this much, but in most instances there are _associated_ nervous mechanisms and ideas that are highly important in determining the exact volume, quality, etc., of the tone as related to expression of ideas and feelings according to conventional usage. The breath-stream must in all cases be so employed that there shall be economy of energy--no waste. Waste occurs whenever air escapes to any appreciable extent through the glottis chink, as that implies an imperfect adjustment of the vocal bands and the expiratory current. From this and other points of view it may be said that _he is the best singer who gets the most perfect result with the least expenditure of energy_. It is of the highest importance that during every practice, and every moment of each practice, attention be given to as perfect a result as possible, and that the same method be invariably employed.