See A. Baines, Woodwind Instruments and Their History (rev. ed. 1963); A. Carse, Musical Wind Instruments (2d ed. 1965); R. Donington, Instruments of Music (3d ed. 1970).
All wind instruments use a combination of the first or second or third and the fourth method to extend their register.
Although brass instruments were originally made of brass and woodwind instruments have traditionally been made of wood, the material used to make the body of the instrument is not always a reliable guide to its family type. A more accurate way to determine whether an instrument is brass or woodwind is to examine how the player produces sound. In brass instruments, the player's lips vibrate, causing the air within the instrument to vibrate. In woodwind instruments the player either:
For example, the saxophone is typically made of brass, but is classified as a woodwind instrument due to the method of vibrating the air column (by using a reed).
On the other hand, the wooden cornett (not to be confused with the cornet, which is made of brass) and the serpent are both made of wood (or plastic tubing, in the case of modern serpents), but belong to the family of brass instruments because the vibrating is done by the player's lips.
The bell of a wind instrument is the round, flared opening opposite the mouthpiece. It is found on horns, trumpets and many other kinds of instruments. On brass instruments, the coustical coupling from the bore to the outside air occurs at the bell for all notes, and the shape of the bell optimizes this coupling. On woodwinds, most notes vent at the uppermost open tone holes; only the lowest notes of each register vent fully or partly at the bell, and the bell's function in this case is to improve the consistency in tone between these notes and the others.