The labial consonants, _p_, _b_, _t_, _d_, are believed to have a peculiar influence in securing the "forward position" of the tone. Much the same influence is also ascribed to the vowel _oo_, although many authorities consider _i_ (Italian) the "most forward" vowel. Exercises combining these consonants and vowels are very widely used, on single tones, and on groups of three, four, or five notes. The syllables _boo_, _poo_, _too_, _doo_ are practised, or if the teacher hold to the other "forward" vowel, _bee_, _pee_, _tee_, _dee_; the student is instructed to hold the vowel in the "forward position" secured by the initial consonant. Later on, the "forward" vowel is gradually widened into the other vowels; exercises are sung on _boo-ah_, _doo-ah_, etc. This form of instruction is capable of great elaboration. Many teachers use a wide variety of combinations of these vowels and consonants; but as the basic idea is always the same, this class of exercises calls for no further description. The singer's sensations, notably those of "open throat," "expanded vocal tube," "forward tone," and vibration in the chest, are generally brought to the pupil's attention in this form of exercise. Another set of sounds are held to be specially adapted for securing the use of nasal resonance. These are the letters _m_, _n_, and _ng_, when used for starting a tone, and also the vowel _i_ (Italian). The exercises used are similar in character to those just described. In singing these exercises, the student is supposed to "start the tone high up in the head on the initial _m_ or _n_, and to hold it there, while gradually and smoothly opening the mouth for the vowel," etc. The sensations specially noticed in this type of exercise are the feelings of vibration in the nose and forehead. The "forward tone," as well as the nasal resonance, is supposed to be favored by the practice of these exercises. _Enunciation_ Vocal teachers always recognize the importance of a clear delivery of the text in singing. Correct enunciation is therefore considered in all methods. A few teachers believe that a clear pronunciation helps greatly to establish the correct vocal action. Some even go so far as to say that a clear delivery of the words will of itself insure a correct tone-production. But this theory calls for only passing comment. One has but to turn to the vaudeville stage to see its falsity. For singers of that class, the words are of the utmost importance, while the tone-production is usually of the very worst. A few teachers base their methods on the theory that correct tone-production results necessarily from the singing of "pure vowels." This is no doubt interesting, but still far from convincing. The problem of tone-production is not solved quite so simply.