Euphonium in the context of "Ophicleide"

An orchestra (/ˈɔːrkɪstrə/ ; OR-ki-strə) is a large instrumental ensemble typical of classical music, which combines instruments from different families. There are typically four main sections of instruments:

• The string section, including the violin, viola, cello, and double bass
• The woodwind section, including the flute, oboe, clarinet, bassoon, and occasionally saxophone
• The brass section, including the French horn (commonly known as the "horn"), trumpet, trombone, cornet, and tuba, and sometimes euphonium
• The percussion section, including the timpani, snare drum, bass drum, cymbals, triangle, tambourine, tam-tam and mallet percussion instruments

Other instruments such as the piano, harpsichord, pipe organ, and celesta may sometimes appear in a fifth keyboard section or may stand alone as soloist instruments, as may the concert harp and, for performances of some modern compositions, electronic instruments, and guitars.

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. The term labrosone, from Latin elements meaning "lip" and "sound", is also used for the group, since instruments employing this "lip reed" method of sound production can be made from other materials like wood or animal horn, particularly early or traditional instruments such as the cornett, alphorn or shofar.

There are several factors involved in producing different pitches on a brass instrument. Slides, valves, crooks (though they are rarely used today), or keys are used to change vibratory length of tubing, thus changing the available harmonic series, while the player's embouchure, lip tension and air flow serve to select the specific harmonic produced from the available series.

The trombone is a musical instrument in the brass family. As with all brass instruments, sound is produced when the player's lips vibrate inside a mouthpiece, causing 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.

The word trombone derives from Italian tromba (trumpet) and -one (a suffix meaning 'large'), so the name means 'large trumpet'. The trombone has a predominantly cylindrical bore like the trumpet, in contrast to the more conical brass instruments like the cornet, the flugelhorn, the baritone, and the euphonium. The two most frequently encountered variants are the tenor trombone and bass trombone; when the word trombone is mentioned alone; it is mostly taken to mean the tenor model. These are treated as non-transposing instruments, reading at concert pitch in bass clef, with higher notes sometimes being notated in tenor clef. They are pitched in B♭, an octave below the B♭ trumpet and an octave above the B♭ contrabass tuba. The once common E♭ alto trombone became less common as improvements in technique extended the upper range of the tenor, but it is regaining popularity for its lighter sonority. In British brass-band music the tenor trombone is treated as a B♭ transposing instrument, written in treble clef, and the alto trombone is written at concert pitch, usually in alto clef.

The baritone horn, or often simply the baritone, is a valved brass instrument pitched in B♭ in the saxhorn family, employed chiefly in brass, military and concert bands. It has three or sometimes four valves, usually piston valves, although rotary valves are common in Eastern and Central Europe, where it is called the Tenorhorn. The bore is moderately conical, like the E♭ tenor horn and cornet, although narrower than the closely related euphonium and other valved bugles, like the flugelhorn and tuba. It uses a wide-rimmed cup mouthpiece of similar dimensions to trombone and euphonium mouthpieces. Like the trombone and the euphonium, the baritone can be considered either a transposing instrument reading B♭ treble clef, or a non-transposing instrument in bass clef.

In British brass bands, the standard instrumentation includes parts for two baritones, in addition to two euphoniums. In US concert band music there is often a part marked baritone, but these parts are commonly intended for, and played on, the euphonium. A baritone can also play music written for a trombone due to similarities in timbre and range.

The euphonium repertoire consists of solo literature and parts in band or, less commonly, orchestral music written for the euphonium. Since its invention in 1843, the euphonium has always had an important role in ensembles, but solo literature was slow to appear, consisting of only a handful of lighter solos until the 1960s. Since then, however, the breadth and depth of the solo euphonium repertoire has increased dramatically.