Modern brass instruments generally come in one of two families:
- Valved brass instruments use a set of valves (typically three or four but as many as seven or more in some cases) operated by the player's fingers that introduce additional tubing, or crooks, into the instrument, changing its overall length. This family includes all of the modern brass instruments except the trombone: the trumpet, horn (also called French horn), euphonium, and tuba, as well as the cornet, flugelhorn, tenor horn (alto horn), baritone horn, sousaphone, and the mellophone. 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; the latter are the norm for the horn (except in France) and are also common 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, in general, become functionally obsolete for practical purposes. Instruments of both types, however, are sometimes used for period-instrument performances of Baroque or Classical pieces. In more modern compositions, they are occasionally used for their intonation or tone color.
- Natural brass instruments only play notes in the instrument's harmonic series. These include the bugle and older variants of the trumpet and horn. The trumpet was a natural brass instrument prior to about 1795, and the horn before about 1820. In the 18th century, makers developed interchangeable crooks of different lengths, which let players use a single instrument in more than one key. Natural instruments are still played for period performances and some ceremonial functions, and are occasionally found in more modern scores, such as those by Richard Wagner and Richard Strauss.
- 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, ophicleide, keyed bugle and keyed trumpet. They are more difficult to play than valved instruments.
Bore taper and diameter
Brass instruments may also be characterised by two generalizations about geometry of the bore, that is, the tubing between the mouthpiece and the flaring of the tubing into the bell. Those two generalizations are with regard to
- the degree of taper or conicity of the bore and
- the diameter of the bore with respect to its length.
Cylindrical vs. conical bore
While all modern valved and slide brass instruments consist in part of conical and in part of cylindrical tubing, they are divided as follows:
- Cylindrical bore brass instruments are those in which approximately constant diameter tubing predominates. Cylindrical bore brass instruments are generally perceived as having a brighter, more penetrating tone quality compared to conical bore brass instruments. The trumpet, and all trombones are cylindrical bore. In particular, the slide design of the trombone necessitates this.
- Conical bore brass instruments are those in which tubing of constantly increasing diameter predominates. Conical bore instruments are generally perceived as having a more mellow tone quality than the cylindrical bore brass instruments. The "British brass band" group of instruments fall into this category. This includes the flugelhorn, cornet, tenor horn (alto horn), baritone horn, horn, euphonium and tuba. Some conical bore brass instruments are more conical than others. For example, the flugelhorn differs from the cornet by having a higher percentage of its tubing length conical than does the cornet, in addition to possessing a wider bore than the cornet. In the 1910s and 1920s, the E.A. Couturier company built brass band instruments utilizing a patent for a continuous conical bore without cylindrical portions even for the valves or tuning slide.
Whole-tube vs. half-tube
The second division, based on bore diameter in relation to length, determines whether the fundamental tone or the first overtone is the lowest partial practically available to the player:
||Neither the horns nor the trumpet could produce the 1st note of the harmonic series ... A horn giving the C of an open 8 ft organ pipe had to be 16 ft (5 m). long. Half its length was practically useless ... it was found that if the calibre of tube was sufficiently enlarged in proportion to its length, the instrument could be relied upon to give its fundamental note in all normal circumstances. – Cecil Forsyth, Orchestration, p. 86
- Whole-tube instruments have larger bores in relation to tubing length, and can play the fundamental tone with ease and precision. The tuba and euphonium are examples of whole-tube brass instruments.
- Half-tube instruments have smaller bores in relation to tubing length and cannot easily or accurately play the fundamental tone. The second partial (first overtone) is the lowest note of each tubing length practical to play on half-tube instruments. The trumpet and horn are examples of half-tube brass instruments.
For half tube instruments the 'fundamental', although half the frequency of the second harmonic, is in fact a pedal note rather than a true fundamental
Other brass instruments
The instruments in this list fall for various reasons outside the scope of much of the discussion above regarding families of brass instruments.