Musical ensemble

Music ensembles typically have a leader. In jazz bands, rock and pop groups, and similar ensembles, this is the band leader. In classical music, orchestras, concert bands, and choirs are led by a conductor. In orchestra, the concertmaster (principal first violin player) is the instrumentalist leader of the orchestra. In orchestras, the individual sections also have leaders, typically called the "principal" of the section (e.g., the leader of the viola section is called the "principal viola"). Conductors are also used in jazz big bands and in some very large rock or pop ensembles (e.g., a rock concert that includes a string section, a horn section, and a choir that accompanies a rock band's performance).

Classical chamber music

In Western classical music, smaller ensembles are called chamber music ensembles. The terms duo, trio, quartet, quintet, sextet, septet, octet, nonet, and decet describe groups of two up to ten musicians, respectively. A group of eleven musicians, such as found in The Carnival of the Animals, is called an undecet, and a group of twelve is called a duodecet (see Latin numerical prefixes). A soloist playing unaccompanied (e.g., a pianist playing a solo piano piece or a cellist playing a Bach suite for unaccompanied cello) is not an ensemble because it only contains one musician.

Four parts

Strings

A string quartet consists of two violins, a viola, and a cello. There is a vast body of music written for string quartets, making it an important genre in classical music.

Wind

A woodwind quartet usually features a flute, an oboe, a clarinet, and a bassoon.

Brass

A brass quartet features two trumpets, a trombone, and a tuba (or French horn (more commonly known as "horn")).

Sax

A saxophone quartet consists of a soprano saxophone, an alto saxophone, a tenor saxophone, and a baritone saxophone.

Five parts

The string quintet is a common type of group. It is similar to the string quartet, but with an additional viola, cello, or more rarely, the addition of a double bass. Terms such as "piano quintet" or "clarinet quintet" frequently refer to a string quartet plus a fifth instrument. Mozart's Clarinet Quintet is similarly a piece written for an ensemble consisting of two violins, a viola, a cello, and a clarinet, the last being the exceptional addition to a "normal" string quartet.

Some other quintets in classical music are the wind quintet, usually consisting of flute, oboe, clarinet, bassoon, and horn; the brass quintet, consisting of two trumpets, one horn, a trombone, and a tuba; and the reed quintet, consisting of an oboe, a soprano clarinet, a saxophone, a bass clarinet, and a bassoon.

Six or more instruments

Classical chamber ensembles of six (sextet), seven (septet), or eight musicians (octet) are fairly common; the use of latinate terms for larger groups is rare, except for the nonet (nine musicians). In most cases, a larger classical group is referred to as an orchestra of some type or a concert band. A small orchestra with fifteen to thirty members (violins, violas, four cellos, two or three double basses, and several woodwind or brass instruments) is called a chamber orchestra. A sinfonietta usually denotes a somewhat smaller orchestra (though still not a chamber orchestra). Larger orchestras are called symphony orchestras (see below) or philharmonic orchestras.

A pops orchestra is an orchestra that mainly performs light classical music (often in abbreviated, simplified arrangements) and orchestral arrangements and medleys of popular jazz, music theater, or pop music songs. A string orchestra has only string instruments, i.e., violins, violas, cellos, and double basses.

A symphony orchestra is an ensemble usually comprising at least thirty musicians; the number of players is typically between fifty and ninety-five and may exceed one hundred. A symphony orchestra is divided into families of instruments. In the string family, there are sections of violins (I and II), violas, cellos (often eight), and basses (often from six to eight). The standard woodwind section consists of flutes (one doubling piccolo), oboes (one doubling English horn), soprano clarinets (one doubling bass clarinet), and bassoons (one doubling contrabassoon). The standard brass section consists of horns, trumpets, trombones, and tuba. The percussion section includes the timpani, bass drum, snare drum, and any other percussion instruments called for in a score (e.g., triangle, glockenspiel, chimes, cymbals, wood blocks, etc.). In Baroque music (1600–1750) and music from the early Classical period music (1750–1820), the percussion parts in orchestral works may only include timpani.

A wind orchestra or concert band is a large classical ensemble generally made up of between 40 and 70 musicians from the woodwind, brass, and percussion families, along with the double bass. The concert band has a larger number and variety of wind instruments than the symphony orchestra but does not have a string section (although a single double bass is common in concert bands). The woodwind section of a concert band consists of piccolo, flutes, oboes (one doubling English horn), bassoons (one doubling contrabassoon), soprano clarinets (one doubling E♭ clarinet, one doubling alto clarinet), bass clarinets (one doubling contrabass clarinet or contra-alto clarinet), alto saxophones (one doubling soprano saxophone), tenor saxophone, and baritone saxophone. The brass section consists of horns, trumpets or cornets, trombones, euphoniums, and tubas. The percussion section consists of the timpani, bass drum, snare drum, and any other percussion instruments called for in a score (e.g., triangle, glockenspiel, chimes, cymbals, wood blocks, etc.).

Less well known is the large symphonic accordion orchestra. Typically, it includes between 50 and 100 musicians whose free-bass instruments are individually re-tuned in order to recreate the full range of orchestral sounds and timbers required for the performance of traditional Western classical music.

When orchestras perform baroque music (from the 17th century and early 18th century), they may also use a harpsichord or pipe organ, to play the continuo part. When orchestras perform Romantic-era music (from the 19th century), they may also use harps or unusual instruments such as the wind machine or cannons. When orchestras perform music from the 20th century or the 21st century, occasionally instruments such as electric guitar, theremin, or even an electronic synthesizer may be used.