Sound is generated by different methods in the aerophones designated as flutes and reeds in the Sachs-Hornbostel system. In flutes, the airstream is directed against a sharp edge; in reeds, the air column in the tube is caused to vibrate between beating parts of a multiple reed or between a beating single reed and a mouthpiece.

Essential to sound production in reedpipes is the reed itself. Those used on most Western instruments are typically made from the stems of the large semitropical grass Arundo donax, commonly referred to by wind players as cane, grown on the Mediterranean coasts of France, Spain, and Italy. (Substitutes for cane—wood, whalebone, silver, and plastic—also have been tried.) Seasoned over a period of years, cane reeds may be purchased finished or be made by the players themselves.

The double reed for an oboe or a bassoon is made from a strip of cane about twice the length of the finished reed. The inner surface is gouged thin, shaped to be narrower at the ends, and notched in the middle. The reed is then soaked in water and folded in half at the notch. The free ends are bound with thread and, for oboes and English horns, mounted on a short tapered metal tube called a staple. A bassoon reed is bound with thread and wire over a steel mandrel, which is later removed to leave a hollow rounded stem. To finish the reed, the halves are separated at the notch and the tips scraped to a feather edge on the outside. The form and degree of “scrape” applied to the tip of the reed have a profound influence on its behaviour and may vary a great deal from player to player. In playing, the double reed of the oboe and the bassoon is held by the tension of the lips drawn in over the teeth. The opening between the two blades of the reed alternately opens and closes with the pressure of the breath to generate the pulsations in the tube.

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The single reed for the clarinet is made from a slip cut from the stem of A. donax. After being trimmed, the reed is flattened on the inner side, while the end of the rounded outer side is scraped down to a feather edge. The thick end of the reed is attached, flat side down, to the mouthpiece by a metal ligature or length of twine. In playing, the thin end of the reed vibrates, alternately closing and opening the space between the reed and the mouthpiece. The vibration carries through the wedged-shaped tone chamber in the mouthpiece and into the air column in the tube.

The body of some folk instruments is itself a length of reed, made into an instrument by cutting and raising a rectangular tongue from the tube below a natural knot. The tongue is sometimes kept from closing down completely by inserting a hair at the base of the cut.

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Because the tubes of flutes and reed instruments (in contrast to those of trumpet-type aerophones) are short in relation to their diameter, they are generally capable of sounding the fundamental and respond best to pitches low in the overtone series. To play in the upper register, the player must overblow, breaking the air column into parts, each of which vibrates at a frequency that is in direct proportion to the fundamental. Oboes, bassoons, and saxophones—all open tubes with conical bores—overblow at the octave; clarinets, whose cylindrical bore acts as a closed pipe, overblow at the 12th.

In overblowing, the player tightens his lips on the reed. Increasing lip pressure is not always sufficient by itself, however, and a variety of techniques and mechanisms have been developed to assist the player in making the notes of the upper register emerge clearly and instantaneously. For example, on flutes and bassoons, the first finger hole is positioned so that, when it is opened on certain high pitches, low partials are prevented from forming; opening a special key on the clarinet, the saxophone, and the modern oboe serves the same purpose. Overblowing is not a universal practice: the double and single reeds of some non-Western and early European reedpipes are inserted directly into the oral cavity or are covered by a reed cap and hence, being uncontrolled by the lips, do not overblow.

Because of the acoustic characteristics of flutes and reeds, only a few pitches are available on instruments lacking finger holes. Thus, instruments with finger holes are known in most cultures, as are fingering systems. Typical of such systems in the West is the six-hole system, so named because the six finger holes of the Baroque transverse flute and oboe—there were no thumbholes—were controlled by the first, second, and third fingers of both hands. (The left hand normally took the higher position on the pipe, but this did not become standard until the mid-18th century.) Both instruments were pitched in D and sounded d (the D below middle C) when all six finger holes were covered. Lifting the fingers one by one, beginning with the lowest, shortened the sounding length of the instruments and produced e, f♯, g, a, b, and c♯—the remaining notes of the D-major scale; the octave (d′) was overblown.

On six-hole transverse flutes and oboes, chromatic pitches were obtained by closing one or more holes below an open one, a technique known as cross-fingering. For example, to produce f rather than f♯, the player uncovered the fifth hole with the second finger of his right hand while keeping the sixth hole (and the first through fourth holes) covered. (Because this arrangement of the fingers looked vaguely like the tines of a fork, some musicians call it a fork fingering.) With the six-hole configuration, however, no cross-fingering could produce e♭/d♯, because there was no hole to cover below the fundamental, d. Consequently, a seventh hole was bored between the sixth and the end of the transverse flute and oboe; it was covered by a closed key controlled by the fourth finger of the right hand. (A closed key covers the hole when at rest.)

In the late 18th century, additional keys were introduced to ease various difficulties of fingering and intonation. At first, open and closed keys were fitted to instruments through slots cut in rings or knobs of wood left after the body of the instrument was turned on a lathe; the key was secured in the slot with a metal pin. In the first quarter of the 19th century, as the number of keys increased, this type of mounting became increasingly inconvenient for builders. Brass saddles, which included the key mount, came to replace wooden knobs, first on bassoons and later on other woodwinds. Both these methods of affixing keys were eventually superseded by the use of metal pillars screwed directly into the wood, to which were attached the key and the axle. In addition, 19th-century reformers such as Theobald Boehm made other, more radical changes in instrument construction that, most notably, allowed the simultaneous closure of holes that lay at some distance from each other. (For a more extensive discussion of Boehm’s landmark modifications to the flute and other woodwind instruments, see The history of Western wind instruments: The Romantic period.) Changes of the type Boehm championed, along with the constantly expanding key system, brought with them a transformation in tone quality, as the valves did to the brass instruments. Although some connoisseurs consider these changes regrettable, they have made possible technical dexterity in all keys.