Image of a trumpet.

A brass instrument is a musical instrument whose tone is produced by vibration of the lips as the player blows into a tubular resonator (mouthpiece). They are also called labrosones, literally meaning "lip-vibrated instruments" (Baines, 1993).

The view of most scholars (see organology) is that the term "brass instrument" should be defined by the way the sound is made, as above, and not by whether the instrument is actually made of brass. Thus, as exceptional cases one finds brass instruments made of wood, like the cornett, and woodwind instruments made of brass, like the saxophone.

Families of brass instruments

Modern brass instruments generally come in one of two families:

Valved brass instruments use a set of valves (typically 3 or 4 but as many as 7 or more in some cases) operated by the player's fingers that introduce additional tubing into the instrument, changing its overall length. This family includes all of the modern brass instruments except the trombone: the trumpet, horn, euphonium, and tuba, as well as the cornet, flugelhorn, baritone horn, sousaphone, mellophone, and the old saxhorn. As valved instruments are predominant among the brasses today, a more thorough discussion of their workings can be found below. The valves are usually piston valves, but can be rotary valves. Rotary valves are the norm for the horn and are also prevalent on the tuba.

Slide brass instruments use a slide to change the length of tubing. The main instruments in this category are the trombone family, though valve trombones are occasionally used, especially in jazz. The trombone family's ancestor the sackbut and the folk instrument bazooka are also in the slide family.

There are two other families that have now become functionally obsolete, though instruments of both types are sometimes used for period-instrument performances of Baroque- or Classical-era pieces.

Natural brass instruments, where the player can only play notes in the instrument's harmonic series, for example the bugle. The trumpet was a natural brass instrument prior to about 1795, and the horn before about 1820. Natural instruments are still played for some ceremonial functions, as well as period performances.

Keyed or Fingered brass instruments used holes along the body of the instrument, which were covered by fingers or by finger-operated pads (keys) in a similar way to a woodwind instrument. These included the cornett, serpent and keyed trumpet. They are more difficult to play than valved instruments.

Some other wind instruments

Alphorn (wood)
Conch (shell)
Didgeridoo (wood, Australia)
Natural horn
Shofar (horn)
Vladimirsky rozhok (wood, Russia)
Wagner tuba

Valves

Piston valve

Rotary valve

Slide Slide

As noted above, valves allow brass players to change pitches A piston valve is a device used to change the pitch of a brass instrument; three or more piston valves can be found on trumpets, tubas, and the like. When opened ("pressed" and "pushed down"), each valve changes the pitch by diverting the air stream through additional tubing, thus lengthening the instrument and lowering the harmonic series on which the instrument is vibrating. The additional tubing usually features a short tuning slide of its own for fine adjustment of the valve's tuning, except when it is too short to make this practicable.

An alternate to the piston valve is the rotary valve.

The first piston valve instruments were developed just after the start of the 19th century. The Stölzel valve (invented by Gottfried Heinrich Stölzel in 1814) was an early variety. In the mid 19th century the Vienna valve was an improved design. However most professional musicians preferred rotary valves for quicker, more reliable action, until better designs of piston valves were mass manufactured towards the end of the 19th century. Since the early decades of the 19th century, piston valves have been the most common on brass instruments.

The following list shows how each valve or combination of valves will affect the pitch from the fundamental; this is true of all brass instruments.

second valve - one half step
first valve - one whole step
first and second valves - one and a half steps. This is also achievable by third valve alone but the note will usually be flat (see below).
second and third valves - two whole steps
first and third valves - a perfect fourth, or two and a half steps. This combination will be noticably sharp unless some means of compensation is used.
first, second, and third valves - a tritone, or three whole steps. Will be very sharp unless some means of compensation is used.

Note that the mentioned tuning deficiencies are unavoidable; they are inherent in the construction of the instrument (see below).

In most trumpets and cornets, the "compensation" must be provided by extending the third valve slide with the fourth finger to lower the pitch of 1-3 and 1-2-3 combinations.

In instruments with a fourth valve, such as tubas, euphoniums, and piccolo trumpets, that valve lowers the pitch by a perfect fourth; this is used partly to compensate for the sharpness of the final two valve combinations (4 for 1-3, 2-4 for 1-2-3). Of course, the other three valves can be used as normal to lower the pitch in combination with the fourth valve, so a fourth valve also extends the instrument's range downward by a perfect fourth, though with increasingly severe intonation problems.

When folur-valved models without any kind of compensation play in the corresponding register, the sharpness becomes so severe that players must finger the note a half-step below the one they are trying to play. This eliminates the note a half-step above their open fundamental.

To correct for these problems, manufacturers of low brass instruments may choose one or a combination of four basic approaches, whose respective merits are subject to debate:

Compensation system

Each of the first two (or three) valves has an additional set of tubing extending from the back of the valve. When the third (or fourth) valve is depressed in combination with another one, the air is routed through both the usual set of tubing plus the extra one, so that the pitch is lowered by an appropriate amount. This allows compensating instruments to play with accurate intonation in the octave below their open second partial, which is critical for tubas and euphoniums in much of their repertoire.

There are also compensating French horns. While these are popular with beginners as they weigh less, most advanced players disapprove of them, criticizing their sound and response.

Additional valves

Initially, compensated instruments tended to sound stuffy and blow less freely due to the air being doubled back through the main valves. In early designs, this led to sharp bends in the tubing and other obstructions of the air-flow. Some manufacturers therefore preferred adding more 'straight' valves instead, which for example could be pitched a little lower than the 2nd and 1st valves and were intended to be used instead of these in the respective valve combinations. While no longer featured in euphoniums for decades, professional tubas are still built like this, with five valves being the norm on CC- and BBb-tubas and five or six valves on F-tubas.

Additional sets of slides on each valve

Another approach was the addition of two sets of slides for different parts of the range. There used to be euphoniums and tubas built like this, but today, this approach has become highly exotic for all instruments - except French horns for which it is the norm, usually in a double, sometimes even triple configuration.

Trigger mechanism

A mechanical lever is provided to pull out the main tuning slide or a valve slide. This is found as an additional intonation aid on some euphoniums and on many five-valved F-Tubas.

Sound production in brass instruments

Because the player of a brass instrument has direct control of the prime vibrator (the lips), brass instruments exploit the player's ability to select the harmonic at which the instrument's column of air will vibrate. By making the instrument about twice as long as the equivalent woodwind instrument and starting with the second harmonic, players can get a good range of notes simply by varying the tension of their lips (see embouchure). Brass players call each harmonic a "partial" because it causes only a part of the tubing to vibrate (whereas at the fundamental the entire tubing will vibrate).

Most brass instruments are fitted with a removable mouthpiece. Different shapes, sizes and styles of mouthpiece may be used to suit different embouchures, or to more easily produce certain tonal characteristics. Trumpets are characteristically fitted with a cupped mouthpiece, while horns are fitted with a conical mouthpiece.

One interesting difference between a woodwind instrument and a brass instrument is that woodwind instruments are non-directional. This means that the sound produced propagates in all directions with approximately equal volume. Brass instruments, on the other hand, are highly directional, with most of the sound produced traveling straight outward from the bell. This difference makes it significantly more difficult to record a woodwind instrument accurately. It also plays a major role in some performance situations, such as in marching bands.

Pedal Tone

All brass instruments that have cylindrical bores will naturally produce only odd-numbered partials. This is due to the fact that all brass instruments are closed at one end (the mouth end), and therefore obey the physics of stopped air columns. Since instruments such as the trumpet and trombone are only able to play 7 distinct semitones in a given partial, they need access to all the partials in order to play chromatically in the low registers. This deficiency is fixed by the special shapes of the bell and mouthpiece. This causes every partial to become available except for the fundamental (Bb1 on the trombone and Bb2 on the trumpet). However, if the player vibrates his/her lips at the fundamental frequency, the resonance of the instrument will support all of the overtones of the note, and the note will sound. This is what is referred to as the pedal tone, or missing fundamental. Since the instrument does not actually resonate at the fundamental frequency of the note heard, this partial has a slightly different timbre than the other partials.

Didactics

Children may start to learn a brass instrument as soon as all their permanent teeth have arrived, usually at age 11. It is possible to start earlier, but as long as the teeth are still changing, the embochure will have to be adjusted occasionally and pressure on the lips and teeth should be avoided especially carefully.

References

Baines, Anthony (1993).

External links

The traditional manufacture of brass instruments, a 1991 video (Real Player format) featuring maker Robert Barclay; from the web site of the Canadian Museum of Civilization.
The Orchestra: A User's Manual - Brass
Brass-Forum.co.uk UK based brass discussion forum.
Brassmusic.Ru — Russian Brass Community
Acoustics of Brass Instruments from Music Acoustics at the University of New South Wales

Categories: Brass instruments

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