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In music, the bore of a wind instrument (including woodwind and brass) is its interior chamber. This defines a flow path through which air travels, which is set into vibration to produce sounds. The shape of the bore has a strong influence on the instrument's timbre.
The cone and the cylinder are the two idealized shapes used to describe the bores of wind instruments. Other shapes are not generally used, as they tend to produce dissonant, anharmonic overtones and an unmusical sound. Instruments may consist of a primarily conical or cylindrical tube, but begin in a mouthpiece, and end in a rapidly-expanding "flare" or "bell". This flare reduces the acoustic impedance mismatch between the instrument and the air, allowing the instrument to transmit sound to the air more effectively. [1]
These shapes affect the prominence of harmonics associated with the timbre of the instrument. A bore that flares from the mouthpiece reduces resistance to the breath, while a bore that narrows from the mouth increases it, compared to a cylinder.
The diameter of a cylindrical bore remains constant along its length. The acoustic behavior depends on whether the instrument is stopped (closed at one end and open at the other), or open (at both ends). For an open pipe, the wavelength produced by the first normal mode (the fundamental note) is approximately twice the length of the pipe. The wavelength produced by the second normal mode is half that, that is, the length of the pipe, so its pitch is an octave higher; thus an open cylindrical bore instrument overblows at the octave. This corresponds to the second harmonic, and generally the harmonic spectrum of an open cylindrical bore instrument is strong in both even and odd harmonics. For a stopped pipe, the wavelength produced by the first normal mode is approximately four times the length of the pipe. The wavelength produced by the second normal mode is one third that, i.e. the 4/3 length of the pipe, so its pitch is a twelfth higher; a stopped cylindrical bore instrument overblows at the twelfth. This corresponds to the third harmonic; generally the harmonic spectrum of a stopped cylindrical bore instrument, particularly in its bottom register, is strong in the odd harmonics only. Modern brass instruments however generally make use of the full length of the instrument for every pitch, and are therefore significantly affected by the effects of the mouthpiece and bell. These modify the instrument's resonances to closely resemble that of a conical pipe, even if the bore is mostly cylindrical. [2]
Instruments having a cylindrical, or mostly cylindrical, bore include:
The diameter of a conical bore varies linearly with distance from the end of the instrument. A complete conical bore would begin at zero diameter—the cone's vertex. However, actual instrument bores approximate a frustum of a cone. The wavelength produced by the first normal mode is approximately twice the length of the cone measured from the vertex. The wavelength produced by the second normal mode is approximately equal to the length of the cone, so its pitch is an octave higher. Therefore, a conical bore instrument, like one with an open cylindrical bore, overblows at the octave and generally has a harmonic spectrum strong in both even and odd harmonics.
Instruments having a conical, or approximately conical, bore include:
Sections of the bores of woodwind instruments deviate from a true cone or a cylinder. For example, although oboes and oboes d'amore are similarly pitched, they have differently shaped terminal bells. Accordingly, the voice of the oboe is described as "piercing" as compared to the more "full" voice of the oboe d'amore.
Although the bore shape of woodwind instruments generally determines their timbre, the instruments' exterior geometry typically has little effect on their voice. In addition, the exterior shape of woodwind instruments may not overtly match the shape of their bores. For example, while oboes and clarinets may outwardly appear similar, oboes have a conical bore while clarinets have a cylindrical bore.
The bore of a baroque recorder has a "reversed" taper, being wider at the head and narrower at the foot of the instrument. [3] Most contemporary recorders also have such a conical bore as they are made very similar to baroque recorders. However, multiple renaissance, medieval and also modern recorders have a cylindrical bore. Some tin flageolets also have a reverse taper.
Brass instruments also are sometimes categorized as conical or cylindrical, though most in fact have cylindrical sections between a conical section (the mouthpiece taper or leadpipe) and a non-conical, non-cylindrical flaring section (the bell). Benade gives the following typical proportions: [4]
| Trumpet | Trombone | Horn | |
|---|---|---|---|
| Mouthpiece taper | 21% | 9% | 11% |
| Cylindrical part | 29% | 52% | 61% |
| Bell | 50% | 39% | 28% |
These proportions vary as valves or slides are operated; the above numbers are for instruments with the valves open or the slide fully in. This deviation from standard models of cylindrical and conical tubes means normal mode frequencies of brass instruments do not correspond to integer multiples of the first mode, which is not used for playing. The higher modes however do correspond fairly to integer multiples of a "fictitious fundamental" which can often still be played as a pedal tone. [5] Players of brasses (in contrast to woodwinds) are able to "lip" notes up or down substantially, and on some instruments make use of privileged frequencies (pedal tones and false tones), to obtain in-tune notes outside of the range allowed for by the normal modes. [4]
A brass instrument is a musical instrument that produces sound by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips. Brass instruments are also called labrosones or labrophones, from Latin and Greek elements meaning 'lip' and 'sound'.
The clarinet is a single-reed musical instrument in the woodwind family, with a nearly cylindrical bore and a flared bell.
A harmonic series is the sequence of harmonics, musical tones, or pure tones whose frequency is an integer multiple of a fundamental frequency.
The oboe is a type of double-reed woodwind instrument. Oboes are usually made of wood, but may also be made of synthetic materials, such as plastic, resin, or hybrid composites.
The recorder is a family of woodwind musical instruments in the group known as internal duct flutes: flutes with a whistle mouthpiece, also known as fipple flutes, although this is an archaic term. A recorder can be distinguished from other duct flutes by the presence of a thumb-hole for the upper hand and seven finger-holes: three for the upper hand and four for the lower. It is the most prominent duct flute in the western classical tradition.
The trombone is a musical instrument in the brass family. As with all brass instruments, sound is produced when the player's vibrating lips cause the air column inside the instrument to vibrate. Nearly all trombones use a telescoping slide mechanism to alter the pitch instead of the valves used by other brass instruments. The valve trombone is an exception, using three valves similar to those on a trumpet, and the superbone has valves and a slide.
Woodwind instruments are a family of musical instruments within the greater category of wind instruments.
An overtone is any resonant frequency above the fundamental frequency of a sound. In other words, overtones are all pitches higher than the lowest pitch within an individual sound; the fundamental is the lowest pitch. While the fundamental is usually heard most prominently, overtones are actually present in any pitch except a true sine wave. The relative volume or amplitude of various overtone partials is one of the key identifying features of timbre, or the individual characteristic of a sound.
An aerophone is a musical instrument that produces sound primarily by causing a body of air to vibrate, without the use of strings or membranes, and without the vibration of the instrument itself adding considerably to the sound.
Overblowing is the manipulation of supplied air through a wind instrument that causes the sounded pitch to jump to a higher one without a fingering change or the operation of a slide. Overblowing may involve a change in the air pressure, in the point at which the air is directed, or in the resonance characteristics of the chamber formed by the mouth and throat of the player.
The tenor saxophone is a medium-sized member of the saxophone family, a group of instruments invented by Adolphe Sax in the 1840s. The tenor and the alto are the two most commonly used saxophones. The tenor is pitched in the key of B♭ (while the alto is pitched in the key of E♭), and written as a transposing instrument in the treble clef, sounding an octave and a major second lower than the written pitch. Modern tenor saxophones which have a high F♯ key have a range from A♭2 to E5 (concert) and are therefore pitched one octave below the soprano saxophone. People who play the tenor saxophone are known as "tenor saxophonists", "tenor sax players", or "saxophonists".
The rackett, raggett, cervelas, or sausage bassoon is a Renaissance-era double reed wind instrument, introduced late in the sixteenth century and already superseded by bassoons at the end of the seventeenth century.
An organ pipe is a sound-producing element of the pipe organ that resonates at a specific pitch when pressurized air is driven through it. Each pipe is tuned to a note of the musical scale. A set of organ pipes of similar timbre comprising the complete scale is known as a rank; one or more ranks constitutes a stop.
The xaphoon is a chromatic keyless single-reed woodwind instrument invented in 1972, and a registered trademark of its inventor, Brian Lee Wittman. It has a closed cylindrical bore and a very slightly flared bell. The xaphoon has a full chromatic range of two octaves, and overblows at the twelfth like the clarinet.
An acoustic horn or waveguide is a tapered sound guide designed to provide an acoustic impedance match between a sound source and free air. This has the effect of maximizing the efficiency with which sound waves from the particular source are transferred to the air. Conversely, a horn can be used at the receiving end to optimize the transfer of sound from the air to a receiver.
A single-reed instrument is a woodwind instrument that uses only one reed to produce sound. The very earliest single-reed instruments were documented in ancient Egypt, as well as the Middle East, Greece, and the Roman Empire. The earliest types of single-reed instruments used idioglottal reeds, where the vibrating reed is a tongue cut and shaped on the tube of cane. Much later, single-reed instruments started using heteroglottal reeds, where a reed is cut and separated from the tube of cane and attached to a mouthpiece of some sort. By contrast, in a double reed instrument, there is no mouthpiece; the two parts of the reed vibrate against one another. Reeds are traditionally made of cane and produce sound when air is blown across or through them. The type of instruments that use a single reed are clarinets and saxophone. The timbre of a single and double reed instrument is related to the harmonic series caused by the shape of the corpus. E.g. the clarinet is only including the odd harmonics due to air column modes canceling out the even harmonics. This may be compared to the timbre of a square wave.
The guan is a Chinese double reed wind instrument. The northern Chinese version is called guanzi or bili and the Cantonese version is called houguan. It is classified as a bamboo instrument in the Ba Yin system. Unlike other instruments in the double-reed family of woodwinds which mostly have conical bores, such as the Chinese suona or the Western oboe, the guan has a cylindrical bore, giving its distinctive mellow, yet piercing buzz-like timbre.
Acoustic resonance is a phenomenon in which an acoustic system amplifies sound waves whose frequency matches one of its own natural frequencies of vibration.
A reed pipe is an organ pipe that is sounded by a vibrating brass strip known as a reed. Air under pressure is directed towards the reed, which vibrates at a specific pitch. This is in contrast to flue pipes, which contain no moving parts and produce sound solely through the vibration of air molecules. Reed pipes are common components of pipe organs.
A wind instrument is a musical instrument that contains some type of resonator in which a column of air is set into vibration by the player blowing into a mouthpiece set at or near the end of the resonator. The pitch of the vibration is determined by the length of the tube and by manual modifications of the effective length of the vibrating column of air. In the case of some wind instruments, sound is produced by blowing through a reed; others require buzzing into a metal mouthpiece, while yet others require the player to blow into a hole at an edge, which splits the air column and creates the sound.
