A flute is an aerophone that is played by blowing air across a sharp edge in the mouthpiece of the instrument. The flute family is a large family of instruments that includes widely-recognized instruments such as the orchestral flute and piccolo, panpipes, and recorders, as well as unusual instruments such as nose flutes and ocarinas. Although many particular kinds of flutes are not widely known, flutes in general are probably the most common non-percussion instrument found in music traditions around the world.

Flutes are usually (but not always) long, thin cylinders that are open at both ends. (Even if the flute appears to be closed at the mouthpiece end, air can usually escape at the blow hole, making the flute effectively an open-open cylindrical tube instrument.) If the player blows into one end of the cylinder, the flute is called end-blown; if the blow hole is in the side of the instrument, it is side-blown, or transverse. Flutes that are not cylindrical (such as ocarinas) are usually classified as vessel flutes.

There are many different types of flutes played around the world. Some have keys, some just finger holes, some are a collection of tubes, and some are just whistles. The one thing that classifies an instrument as a flute is the mouthpiece, where the sound originates.

Flutes have a sharp edge mouthpiece. The sound is produced by blowing a thin, concentrated stream of air at a sharp edge. The stream of air, instead of splitting smoothly at the sharp edge, vibrates back and forth between one side of the edge and the other. This vibration is picked up, reinforced, and turned into a pretty sound by the rest of the instrument (please see Standing Waves and Wind Instruments for more on this).

The two major families of flutes are the blow hole aerophones, in which the mouth must direct the air stream toward one edge of a blow hole, and the whistle mouthpiece aerophones, in which the player blows into a whistle-type mouthpiece that directs the air toward a sharp edge.

The flute most commonly used in today's Western orchestras and bands is a side-blown, or transverse flute made of metal (or sometimes dark wood). It is a concert-pitch (non-transposing) instrument. Its basic design -particularly its system of keys and fingerings - was developed by Theobald Boehm (1793-1881) of Munich, in the 1830's. Boehm was a concert flautist (flute player), and also a goldsmith who had some understanding of acoustics (the physics of sound). He changed the placement of the fingerholes, enlarged them, and added complex keywork mounted on rods along the body of the instrument. Boehm's design was a distinct improvement on earlier instruments, and the flute is now the most agile of the orchestral woodwinds.

The orchestral flute has a cylindrical bore. Its timbre is dominated by the fundamental harmonic, giving it a very clear, uncomplicated sound.

The flute can usually be disassembled into three sections: the head joint (which includes the mouthpiece), the middle joint, and the foot joint. It has sixteen keys padded with felt to ensure an airtight seal when the key is held down by a finger. When at rest, the key is held open by a small steel spring.

Two other flutes sometimes found in Western music are the piccolo and alto flutes. The flauto piccolo (Italian for "small flute"), in common use since the late eighteenth century, is half the length of a standard flute and plays an octave higher than written. The alto flute is noticeably larger than the standard flute, and its range is a perfect fourth lower. It is a transposing instrument which plays a perfect fourth lower than written.

Both have Boehm-system keywork (in fact, the modern alto flute was developed by Boehm), and the fact that they are transposing instruments means that a flautist doesn't need to learn a new set of fingerings for each instrument. (The fingering for a written C in the staff, for example, will be essentially the same on all three instruments).

Bass flute, a twentieth-century invention, is still quite rare.

The holes in early transverse flutes were spaced to give mean tone tuning. This tuning system was popular in Europe from the sixteenth through the eighteenth centuries, but it made it difficult for one instrument to play well in more than one key. This limited the flute's usefulness to orchestra.

The recorder, a wooden, end-blown, whistle-mouthpiece type flute was very popular in early Western music. It was particularly popular in the Renaissance and Baroque periods. But it is not an ideal orchestral instrument because of its quiet sound.

Meanwhile, the keywork on transverse flutes was gradually being improved (see above), and equal temperament, which allows an instrument to play equally well in all keys, became the accepted tuning standard. At that point, the transverse flute, with its wider range of timbre, pitch, and dynamics, became more popular than the recorder. Eventually the flute replaced the recorder so completely that the recorder nearly died out, until an interest in early music and early instruments helped spark a revival in the twentieth century.

The fife is a small transverse flute that - like the piccolo - sounds an octave higher than the orchestral flute. Its history since the middle ages is one of military rather than concert use, however. There were at one time fife "calls" used as signals (similar to the bugle calls still in use), and fife and drum corps still play military music.

The flute family is also the most widespread aerophone family, with representatives in more Non-Western music traditions around the world than any other non-percussion instrument. Bamboo flutes are common throughout Asia. Panpipes, which have many different-sized tubes bound together rather than finger holes in a single tube, are particularly popular in South America. Many variations of the side-blown and end-blown flutes (including double and triple flutes) have been developed in many cultures. Vessel flutes have been made in many different shapes, including animals and people, out of many different materials, including bone, wood, fruit shells, and pottery. Whistles are usually used for signals rather than music, but bird whistles, which are filled with water to get a bubbling whistle that sounds very much like the trill of a bird, are sometimes found in the percussion section of orchestras and bands. Nose flutes, played with the nose rather than the mouth, are popular in some South Pacific and Indian Ocean countries.

Figure 1: The written range is the same for flute and piccolo. Flutes sound as written; piccolo is a transposing instrument that sounds one octave higher than written.

Flute and Piccolo Range

Flute and piccolo are both very agile instruments that can play very quick notes, large leaps and special effects like trills and flutter-tonguing.

The lowest octave of the range is not loud, and the very lowest notes are rather weak. The very highest notes in the range can be shrill and out of tune.

The piccolo has a very piercing sound; a single piccolo in the upper register can be heard over an entire orchestra.