Choir

A choir (/ˈkwaɪ.ər/) (also known as a chorale or chorus) is a musical ensemble of singers. Choral music, in turn, is the music written specifically for such an ensemble to perform. Choirs may perform music from the classical music repertoire, which spans from the Medieval era to the 2010s, and/or popular music repertoire. Most choirs are led by a conductor, who leads the performances with arm and face gestures.
A body of singers who perform together as a group is called a choir or chorus. The former term is very often applied to groups affiliated with a church (whether or not they actually occupy the choir) and the second to groups that perform in theatres or concert halls, but this distinction is far from rigid. Choirs may sing without instrumental accompaniment, with the accompaniment of a piano or pipe organ, with a small ensemble (e.g., harpsichord, cello and double bass for a Baroque era piece), or with a full orchestra of 70-100 musicians.
The term "Choir" has the secondary definition of a subset of an ensemble; thus one speaks of the "woodwind choir" of an orchestra, or different "choirs" of voices and/or instruments in a polychoral composition. In typical 18th- to 21st-century oratorios and masses, chorus or choir is usually understood to imply more than one singer per part, in contrast to the quartet of soloists also featured in these works.

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Structure
Choirs are often led by a conductor or choirmaster. Most often choirs consist of four sections intended to sing in four part harmony, but there is no limit to the number of possible parts as long as there is a singer available to sing the part: Thomas Tallis wrote a 40-part motet entitled Spem in alium, for eight choirs of five parts each; Krzysztof Penderecki's Stabat Mater is for three choirs of 16 voices each, a total of 48 parts. Other than four, the most common number of parts are three, five, six, and eight.
Choirs can sing with or without instrumental accompaniment. Singing without accompaniment is called a cappella singing (although the American Choral Directors Association discourages this usage in favor of "unaccompanied," since a cappella denotes singing "as in the chapel" and much unaccompanied music today is secular). Accompanying instruments vary widely, from only one instrument (a piano or pipe organ) to a full orchestra of 70-100 musicians; for rehearsals a piano or organ accompaniment is often used, even if a different instrumentation is planned for performance, or if the choir is rehearsing unaccompanied music.
Many choirs perform in one or many locations such as a church, opera house, or school hall. In some cases choirs join up to become one "mass" choir that performs for a special concert. In this case they provide a series of songs or musical works to celebrate and provide entertainment to others.

Types

• Mixed choirs (with male and female voices). This is perhaps the most common type, usually consisting of soprano, alto, tenor, and bass voices, often abbreviated as SATB. Often one or more voices is divided into two, e.g., SSAATTBB, where each voice is divided into two parts, and SATBSATB, where the choir is divided into two semi-independent four-part choirs. Occasionally baritone voice is also used (e.g., SATBarB), often sung by the higher basses. In smaller choirs with fewer men, SAB, or Soprano, Alto, and Baritone arrangements allow the few men to share the role of both the tenor and bass in a single part.
• Male choirs, with the same SATB voicing as mixed choirs, but with boys singing the upper part (often called trebles or boy sopranos) and men singing alto (in falsetto), also known as countertenors. This format is typical of the British cathedral choir.
• Female choirs, usually consisting of soprano and alto voices, two parts in each, often abbreviated as SSAA, or as soprano I, soprano II, and alto, abbreviated SSA.
• Men's choirs, or Male Chorale, usually consisting of two tenors, baritone, and bass, often abbreviated as TTBB (or ATBB if the upper part sings falsetto in alto range). ATBB may be seen in some barbershop quartet music.
• Children's choirs, often two-part SA or three-part SSA, sometimes more voices. This includes boy choirs.Boy choirs typically sing SSA or SSAA, sometimes including a tenor part for boys whose voices are changing.
• Indian music choral group, takes the elements of western music in Indian music. Madras Youth choir is a pioneer in this.

Choirs are also categorized by the institutions in which they operate:

• Church and cathedral choirs
• Collegiate and university choirs
• Community choirs (of children or adults)
• Professional choirs, either independent (e.g. Anúna) or state-supported (e.g., BBC Singers, National Chamber Choir of Ireland, Canadian Chamber Choir, Swedish Radio Choir)
• School choirs
• Signing choirs using sign language rather than voices
• Integrated signing and singing choirs, using both sign language and voices and led by both a signductor and a musical director
• Cambiata choirs, often the same SATB, but with girls singing soprano and alto, along with trebles and cambiatas and boy altos

Some choirs are categorized by the type of music they perform, such as

• Bach choirs
• Barbershop music
• Gospel choirs
• Show choirs, in which the members sing and dance, often in performances somewhat like musicals
• Symphonic choirs
• Vocal jazz choirs

Arrangements On Stage
There are various schools of thought regarding how the various sections should be arranged on stage.
In symphonic choirs it is common (though by no means universal) to order the choir behind the orchestra from highest to lowest voices from left to right, corresponding to the typical string layout.
In a cappella or piano-accompanied situations it is not unusual for the men to be in the back and the women in front; some conductors prefer to place the basses behind the sopranos, arguing that the outer voices need to tune to each other.
More experienced choirs may sing with the voices all mixed. Sometimes singers of the same voice are grouped in pairs or threes. Proponents of this method argue that it makes it easier for each individual singer to hear and tune to the other parts, but it requires more independence from each singer. Opponents argue that this method loses the spatial separation of individual voice lines, an otherwise valuable feature for the audience, and that it eliminates sectional resonance, which lessens the effective volume of the chorus.
For music with double (or multiple) choirs, usually the members of each choir are together, sometimes significantly separated, especially in performances of 16th-century music. Some composers actually specify that choirs should be separated, such as in Benjamin Britten's War Requiem.
Consideration is also given to the spacing of the singers. Studies have found that not only the actual formation, but the amount of space (both laterally and circumambiently) affects the perception of sound by choristers and auditors. (CT)


(Reference: wikipedia.org)