What defines a choir?

A choir, chorale, or chorus is a musical ensemble of singers. A body of singers who perform together 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. "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 20 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.

Choirs are often led by a conductor or choirmaster. Most often choirs consist of four parts but there is no limit to the number of possible parts: 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[1] discourages this usage in favor of "unaccompanied"). Accompanying instruments can consist of practically any instruments, from one to a full orchestra; for rehearsals a piano or organ accompaniment is often used even if a different instrumentation is planned for performance, or for rehearsing a cappella music. While Eastern Orthodox churches and some synagogues ban the use of instruments, in churches of the western rite the accompanying instrument is almost always an organ.

Beside the leading of singing in which the congregation participates such as hymns and service music, choirs still sing the full propers (introit, gradual, comunion antiphons appropriate for the different times of the liturgical year) at a few churches, chiefly those of the Anglican or Roman Catholic churches; far more common however is the performance of an anthem at the offertory. The Vatican conducts all of its Masses in Latin [citation needed], and its choir mainly made up of religious clergy[citation needed]. They sing a repertory of Latin Chants known as Gregorian Chant. Local Roman Catholic Churches also use at their discretion to have additional orchestral accompanyment. The most noted Roman Catholic Church in the world to use an orchestral accompanyment is Saint Patrick's Cathedral in New York City.

Choirs can be categorized by the voices they include:

* Mixed choirs (i.e., 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.
* Male choirs, with the same SATB voicing as mixed choirs, but with boys singing the upper part (often called treble or boy soprano) and men singing alto (in falsetto), also known as countertenor.
* Female choirs, usually consisting of soprano and alto voices, two parts in each, often abbreviated as SSAA, or as soprano, soprano II, and alto, abbreviated SSA
* Men's choirs, usually consisting of two tenors, baritone, and bass, often abbreviated as TTBB (or ATBB if the upper part sings falsetto in alto range like barbershop music, even though this notation is not normally used in barbershop music). Occasionally, a men's choir will have Basso Profundo, the lowest of all male vocal ranges.
* Children's choirs, often two-part SA or three-part SSA, sometimes more voices.

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

* Church choirs
* College choirs
* School choirs
* Community choirs (of children or adults)
* Professional choirs, either independent (e.g., Chanticleer) or state-supported (e.g., National Chamber Choir of Ireland, Netherlands Chamber Choir, Estonian Philharmonic Chamber Choir, Canadian Chamber Choir, Swedish Radio Choir etc.)

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

* Symphonic choirs
* Vocal jazz choirs
* Show choirs, in which the members sing and dance, often in performances somewhat like musicals

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 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 often sing with the voices all mixed together. 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.

Skills involved in choral singing

Choral singers vary greatly in their ability and performance. The best choral singers possess (among others) the following abilities:

* to sing precisely in tune and with a vocal timbre which complements the other singers;
* to sing at precisely controlled levels of volume, matching the dynamics and expression marked in the score or prescribed by the conductor, and not sing so loudly as to be markedly detectable as an individual voice within the section;
* to sight-read music fluently;
* to read and pronounce the lyrics accurately and in the pronunciation style specified by the leader, whatever the language may be;
* to remain completely alert for long periods, monitoring closely what is going on in a rehearsal or performance;
* to monitor one's own singing and detect errors.
* to accept direction from others for the good of the group as a whole, even when the singer disagrees esthetically with the instructions;

Singers who have perfect pitch require yet other skills:

* to sing music in keys other than that in which it is written, since choirs often sing music in transposed form.
* to stay in tune with the ensemble, even in the event the ensemble modulates slightly away from "perfect" pitch