Flute Acoustics

A flute produces sound when a stream of air directed across the top of a hole in the lip plate bounces in and out of the hole.^[4] Some engineers have called this a fluidic multivibrator, because it forms a mechanical analogy to an electronic circuit called a multivibrator.

The stream beats against the air in a resonator, usually a tube. The player changes the pitch of the flute by changing the effective length of the resonator. This is done either by closing holes, or more rarely, with a slide similar to a trombone's slide. This slide effect can be produced on a modern day flute by just using the head joint and your finger.

To be louder, a flute must use a larger resonator and a wider air-stream. A flute can generally be made louder by making its resonator and tone-holes larger. This is why police whistles, a form of flute, are very wide for their pitch, and why organs can be far louder than concert flutes: an organ pipe's tone-hole may be several inches wide, while a concert flute's is a fraction of an inch.

The air-stream must be flat, and precisely aimed at the correct angle and velocity, or else it will not vibrate. In fippled flutes, a precisely machined slot extrudes the air. In organs, the air is supplied by a regulated blower.

In non-fipple flutes, especially the concert flute and piccolo, the player must form and direct the stream with his or her lips, which is called an embouchure. This allows the player a wide range of expressions in pitch, volume, and timbre, especially in comparison to fipple flutes. However, it also makes the transverse flute immensely more difficult for a beginner to get a full sound out of than fipple flutes such as the recorder. Transverse flutes also take more air to play, which requires deeper breathing and makes circular breathing trickier, but still not impossible.

Generally, the quality called "tone colour" or "timbre" varies because the flute produces harmonics in different intensities. A harmonic is a frequency that is a whole number multiple of a lower register, or "fundamental" tone of the flute. Generally the air-stream is thinner (to vibrate in more modes), faster (providing more energy to vibrate), and aimed across the hole more shallowly (permitting a more shallow deflection of the airstream to resonate).

Almost all flutes can be played in fundamental, octave, tierce, quatre and cinque modes simply by blowing harder and making the air-stream move more quickly and at a more shallow angle. Flute players select their instrument's resonant mode with embouchure and breath control, much as brass players do.

Many believe that the timbre is also affected by the material from which the instrument is made. For instance, instruments made of wood are often believed to be less bright than metal instruments. Different metals are also thought to influence the tone. However, a study in which professional players were blindfolded could find no significant differences between instruments made from a variety of different metals.^[5] In two different sets of blind listening, no instrument was correctly identified in a first listening, and in a second, only the silver instrument was identified by a significant fraction of the listeners. The study concluded that there was 'no evidence that the wall material has any appreciable effect on the sound color or dynamic range of the instrument'. Physicists who study flutes usually agree that relatively small differences in shape are more important than differences in material, because the waves in the air couple only weakly to vibrations in the body. Wooden flutes usually have different shapes from metal instruments. For instance, the junction between the tone hole risers and the bore are usually sharper in wooden instruments, and these sharper edges are expected to have a substantial effect on sound. This does not mean that a gold flute is no better than, say, a brass one, as the gold flute is likely to have been hand-finished by a more proficient craftsman, and by that merit, possess superior acoustic qualities.

Categories of Flute

In its most basic form, a flute can be an open tube which is blown like a bottle. Over time, the increasing demands of musical performance have led to the development of what many people consider the flute, the Western concert flute, which has a complex array of keys and holes.

There are several broad classes of flutes. With most flutes, the musician blows directly onto the edge of the flute. However, some flutes, such as the recorder, tin whistle, whistle, fujara, and ocarina have a duct that directs the air onto the edge (an arrangement that is termed a "fipple"). This gives the instrument a distinct timbre which is different from non-fipple flutes and makes the instrument easier to play, but takes a degree of control away from the musician. Usually, fipple flutes are not referred to as flutes, even though the physics, technique and sound are similar.

Another division is between side-blown (or transverse) flutes, such as the Western concert flute, piccolo, fife, dizi, and bansuri; and end-blown flutes, such as the xiao, ney, kaval, quena, shakuhachi and tonette. The player of a side-blown flute uses a hole on the side of the tube to produce a tone, instead of blowing on an end of the tube. End-blown flutes should not be confused with fipple flutes such as the recorder, which are also played in the same position but have internal ducts. The earliest transverse flute is a chi (篪) flute discovered in the Tomb of Marquis Yi of Zeng at the Suizhou site, Hubei province, China. It dates from 433 BC, of the later Zhou Dynasty. It is of lacquered bamboo with closed ends. It has five stops that are at the flute's side instead of top. Chi flutes are mentioned in Shi Jing, compiled and edited by Confucius.

Flutes may be open on one or both of their ends. The ocarina, pan pipes, police whistle, and bosun's whistle are closed-ended. Open-ended flutes such as the concert flute and the recorder have more harmonics, and thus more flexibility for the player, and brighter timbres. An organ pipe may be either open or closed, depending on the sound desired.

Flutes can be played with several different air sources. Conventional flutes are blown with the mouth, although some cultures use nose flutes. Organs are blown by bellows or fans.

The Western concert flutes

 

An illustration of a Western concert flute

The Western concert flute, a descendant of the 19th century "German flute," is a transverse flute which is closed at the top. Near the top is the embouchure hole, against which the player blows. The flute has circular finger-holes, various combinations of which can be opened or closed by the flautist, by means of a mechanism of keys, to produce the various notes in the flute's playing range. The note produced depends on which finger-holes are opened or closed by the flautist and on how the flute is blown by the flautist. There are two kinds of footjoints for the concert flute: a C Foot shown is the picture above or the B Foot which has an extra hole to make the flute's range go to a low B. With rare exceptions (i.e., flutes with custom-made fingering-systems), the Boehm system is the fingering-system in correspondence with which Western concert flutes are designed and manufactured.

The standard concert flute is pitched in C and has a range of 3 octaves starting from middle C. However, many professional flutes have an extra key to reach the B directly below middle C. This means that the concert flute is one of the highest orchestral instruments, with only the piccolo being higher. Also commonly used in orchestras is the piccolo, a small flute usually pitched one octave above the concert flute. Alto and bass flutes, respectively pitched a perfect fourth and an octave below the concert flute, are used occasionally. Parts for the alto flute are more common than for the bass. Many other sizes of flute and piccolo are used from time to time. Alto and bass flutes are heavier than the normal C flute, so some people find them more difficult to play for longer periods of time. A much-less common instrument of the current pitching system is the treble G flute. An older pitching system, used principally in older wind-band music, includes D-flat piccolos, E-flat soprano flutes (the primary instrument, equivalent to today's concert C flutes), F alto flutes, and B-flat bass flutes.

The modern professional concert flute is generally made of silver, gold, or combinations of the two. Student instruments are usually made of nickel silver, or silver-plated brass. Curved headjoints are also available for student flutes which make the flute shorter making it possible for children as young as 3 years old to play the flute. Wooden flutes and headjoints are more widely available than in the past. Wooden flutes are often designed to produce a warmer tone that is desirable to some people.

The modern concert flute comes with various options. The B-flat thumb key (invented and pioneered by Briccialdi) is practically standard. The B foot joint, however, is an optional extra available on middle-upper end models.

 

A closed hole "Take-down" flute in case

Open hole flutes, also called French flutes, (where some keys have a circular hole through the middle that the player must cover with fingertips) are common among concert-level players, though some flautists (particularly students, but sometimes even professional flutists as well) select closed-hole "plateau" keys. Students often use temporary plugs to cover the holes in the keys until they master the more exact finger-placement that open-hole keys demand. Some people believe that open-hole keys permit louder and clearer sound projection in the flute's lower range. Open-hole keys are also needed for some modern "extended" avant garde pieces, including those requiring the player to play harmonic overtones, or to manipulate "breathy" sounds in addition to the traditional "pure" tone.

Open-hole keys are typical of French technique, championed by the Paris Conservatoire. Another option is the amusingly named "gizmo key", which facilitates C7.

To play the Western concert flute, one holds the flute in a transverse position, and blows across the hole in the mouthpiece. To distinguish separate notes, one pushes down the keys of the flute in distinct fingerings. However, there are a few alternate fingerings (called trill fingerings) that will assist one in playing difficult passages.

 

Playing a transverse flute.

Variation in Materials Used

The Western Concert Flute can be made from a range of metals such as silver (Britannia or Sterling); gold (yellow or rose); platinum (this is normally plated on the outside, with a sterling silver inner tube); and even alloys. They can be either gold on the inside and silver on the outside, or visa versa.

Members of the concert flute family

From high to low, the members of the concert flute family include:

• Piccolo in C or D-flat
• Treble flute in G
• Soprano flute in Eb
• Concert flute (also called C flute, boehm flute, silver flute, or simply flute)
• Flûte d'amour (also called tenor flute) in B-flat or A
• Alto flute in G
• Bass flute in C
• Contra-alto flute in G
• Contrabass flute in C (also called octobass flute)
• Subcontrabass flute in G (also called double contra-alto flute) or C (also called double contrabass flute)
• Double contrabass flute in C (also called octobass flute or subcontrabass flute)
• Hyperbass flute in C (also spelled hyper-bass flute)

Each of the above instruments has its own range. The piccolo is an octave higher in pitch than the concert flute. Like the concert flute, it reads music in C, but sounds one octave higher. The alto flute is in the key of G, and extends the low register range of the flute to the G below middle C. Its highest note is a high G (4 ledger lines above the treble clef staff). The bass flute is an octave lower than the concert flute, and the contrabass flute is an octave lower than the bass flute.

Less commonly seen flutes include the treble flute in G, pitched one octave higher than the alto flute; the soprano flute, between the treble and concert; and the tenor flute or flûte d'amour in B flat or A, pitched between the concert and alto.

The lowest sizes (larger than the bass flute) have all been developed in the 20th century; these include the sub-bass flute, which is pitched in F, between the bass and contrabass; the subcontrabass flute (pitched in G or C), the contra-alto flute (pitched in G, one octave below the alto), and the double contrabass flute in C, one octave lower than the contrabass. The flute sizes other than the concert flute and piccolo are sometimes called harmony flutes.

The Indian Bamboo Flute

The Indian Bamboo Flute, one of the instruments of Indian classical music, developed independently of the western flute. The Hindu god Krishna is said to be a master of the instrument. The Indian flutes are very simple instruments when compared with their western counterparts; they are made of bamboo and are keyless. The Indian concert flutes are available in standard pitches. In Carnatic Music, the pitches are referred by numbers such as 3 1/2, 4, 5, etc., which is counting upwards from the note C which is taken as 1. However, the pitch of a composition is itself not fixed and hence any of the flutes may be used for the concert (as long as the accompanying instruments, if any, are tuned appropriately) and is largely left to the personal preference of the artist.

Two main varieties of Indian flutes are currently used. The first is the Bansuri, which has six finger holes and one blowing hole, is used predominantly in Hindustani music, the music of north India. The second is Venu or Pullanguzhal, which has eight finger holes, is predominantly used in Carnatic music, the music of south India. Presently, the 8 holed flute with crossfingering technique, is common among many carnatic flautists. This was introduced by the eminent flautist T. R. Mahalingam in the mid 20th century. Prior to this, the south Indian flute had only seven finger holes with the fingering standard was developed by Sharaba Shastri of the Palladam school, in the beginning of the 20th century.

The quality of the sound from the flute depends on the specific bamboo used to make it, and it is supposed that the best bamboos are from the Nagarcoil area in South India.

Dvoyanka (Double Flute)

The dvoyanka is a double flute from the Balkans made of a single piece of wood, with six sound holes on one side. It is most frequently made of ash-wood, plum tree, pear tree, cornel or boxwood. The tune is played on the one pipe, which is accompanied by a flat tone on the other pipe. This kind of playing is similar by structure to music played on the kaval. It is also a favorite instrument of shepherds. Line-dances and lively melodies are frequently played on the dvoyanka. It is a known fact that shepherds directed their flocks by their playing, since sheep remember and recognize a melody in time ^{[citation needed]}. A shepherd could “teach” his flock to start from the pen towards the pasture at one melody, and to return to the village in the evening at another. The dvoyanka is similar to the dvojnica, an instrument typical for the regions of Central and Western Serbia and also Serbian regions across the river Drina, which are made and played somewhat differently to the dvoyanka.

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