A processional hymn is a chant

Chant

Chant is the rhythmic speaking or singing of words or sounds, often primarily on one or two pitches called reciting tones. Chants may range from a simple melody involving a limited set of notes to highly complex musical structures Chant (from French chanter) is the rhythmic speaking or singing...

, hymn

Hymn

A hymn is a type of song, usually religious, specifically written for the purpose of praise, adoration or prayer, and typically addressed to a deity or deities, or to a prominent figure or personification...

 or other music sung during the Procession

Procession

A procession is an organized body of people advancing in a formal or ceremonial manner.-Procession elements:...

, usually at the start of a Christian service although occasionally during the service itself. The procession usually contains members of the clergy and the choir

Choir

A choir, chorale or chorus is a musical ensemble of singers. Choral music, in turn, is the music written specifically for such an ensemble to perform.A body of singers who perform together as a group is called a choir or chorus...

 walking behind the processional cross

Processional Cross

A processional cross is a crucifix or cross which is carried in Christian processions. Such crosses have a long history: the Gregorian mission of Saint Augustine of Canterbury to England carried one before them "like a standard", according to Bede. Other sources suggest that all churches were...

. Occasionally, a service will also contain a recessional hymn

Recessional hymn

A recessional hymn is a hymn placed at the end of a service to close it. It is used commonly in the Catholic Church and Anglican Church, an equivalent to the concluding voluntary, which is called a Recessional Voluntary, for example a Wedding Recessional....

, although in the Protestant tradition this is usually an organ voluntary

Voluntary (music)

In music a voluntary is a piece of music, usually for organ, which is played as part of a church service. In English-speaking countries, the music played before and after the service is often called a 'voluntary', whether or not it is titled so....

.

The genre first appears in the early Middle Ages, and is a distinct genre from breviary

Breviary

A breviary is a liturgical book of the Latin liturgical rites of the Catholic Church containing the public or canonical prayers, hymns, the Psalms, readings, and notations for everyday use, especially by bishops, priests, and deacons in the Divine Office...

 hymns, often containing a refrain

Refrain

A refrain is the line or lines that are repeated in music or in verse; the "chorus" of a song...

. With its longer cathedrals and churches, England was particularly rich in these and several are to be found in the Sarum Processional.