The mouthpiece having been placed on the lips, the mouth should partly open at the sides, and the tongue retire, in order to allow the air to penetrate into the lungs. The stomach ought not to swell, but rather, on the contrary, to recede in proportion as the chest is dilated by the aspiration.
The tongue should then advance against the teeth of the upper jaw, in such a way as to hermetically close the mouth, as though it were a valve intended to keep the column of air in the lungs.
The instant the tongue recedes, the air which was pressing against it precipitates itself into the instrument, and determines the vibrations which produce the sound. The stomach should then gradually resume its primitive (previous) position, in proportion as the chest is lightened by the diminution of the air in the lungs.
The breathing ought to be regulated by the length of the passage to be executed. In short phrases, if the breath be too strongly taken, or too often repeated, it produces a suffocation* resulting from the weight of the column of air pressing too heavily on the lungs. The student should therefore, as early as possible learn to manage his regulation so skillfully as to reach the end of a long phrase without depriving a single note of its full power and firmness.
* To limit the effects of this suffocation (or feeling of drowning) when several longs phrases are played one after the other, it can be helpful to exhale stale air from the lungs before inhaling for the next phrase. Stale air (air that has been depleted of oxygen) in the lungs is the primary cause for feeling suffocated, even panic, at the end of long phrases.