In instruments changes in the length and form of the resonance chambers affect the pitch as well as the quality of the tone. This is demonstrated in the trombone, French horn, and other wind instruments. The lengthening of the tube of the trombone lowers the pitch of the tone, and the projection of the hand of the performer into the bell of the French horn has the effect of raising the pitch of the sound. If the variation in length or form is only slight, the result is sharp or flat, and the instrument is out of tune. In the human instrument all the organs act together as a unit; so the fact that the cavities alone may affect the pitch is practically of no great significance. THE TONGUE The tongue and the lips are the articulating organs, and the former has an important part to play in altering through its movements the shape of the mouth cavity. The tip of the tongue should habitually rest against the under front teeth. The tip of the tongue, however, must frequently touch the roof of the mouth near the upper front teeth, as when pronouncing the consonants _c_, _d_, _g_ or _j_, _l_, _n_, _s_, and _t_. The back part of the tongue must rise a little to close against the soft palate when pronouncing _g_ hard, and _k_, and hard _c_, _q_, and _x_. The soft palate comes down so far to meet the tongue that the elevation of the latter need be but very slight. When speaking, the demand is not so imperative, but when singing, the body of the tongue should lie as flat as possible, so as to enlarge the mouth, especially when giving the vowel sounds. If the tongue is sometimes disposed to be unruly, it is the result of rigidity or misplaced effort in the surrounding parts. This tendency will only be aggravated by artificial restraint of any kind. The true way is to dismiss tongue consciousness, _let go_, and a normal flexibility will easily manifest itself. THE LIPS The lips, equally with the tongue, are organs of articulation. The upper lip is the principal factor of the two; the under lip seems to follow the lead of the upper. The lips need much training, and it can readily be given them. While practising to educate the lips, both lips should be projected forward and upward, at the same time pronouncing the word "too." Bring the edge of the upper lip as high toward the nose as possible in practice. This will bring the corners of the mouth forward and lift the lips clear and free from the teeth, and thus add one more resonance cavity. This position of the lips also gives freedom for pronunciation. "The upper lip plays the most active part in the shaping of the vowels. It should never be drawn against the teeth when producing vowel tones; indeed, there should be often a little space between the upper lip and the teeth, so that the vibrations of the sound-waves can have free play." THE NOSTRILS