Gregorian Chant, also known as plainchant or plainsong, is an ancient form of Christian liturgical music. Plainsong has been around as long as the Christian church has, and was first catalogued and standardized by Pope Gregory I in the late sixth and early seventh centuries. The sound is monophonic (all voices sing the same note, with no harmony) and in eight set modes, and the chants are performed with simple, generally unaccented rhythm. The plainness of the music is intended to help churchgoers move quietly into a meditative, prayerful state, and for many hundreds of years, plainchant was the only kind of music allowed in church services for that reason -- other music was thought to be too distracting and too un-sacred. The traditional Gregorian Chants take their lyrics primarily from the psalms and from the ancient words of the Latin Mass.
Chant was the CD that started the surprising Gregorian Chant craze that begun in the mid-1990s. The ancient Santo Domingo Abbey in Burgos, Spain, is home to an order of Benedictine Monks who have been singing Gregorian Chant in their worship services since the eleventh century. They've recorded a number of albums, but this one happened to catch the fancy of a fairly large listening public. It contains a nice variety of modes and chant styles, and is generally considered the go-to first album for anyone interested in Gregorian Chant.
Konrad Ruhland was an eminent German musicologist who died in 2010. He had a lifelong interest in Gregorian Chant and other lesser-known forms of plainsong (and indeed, despite their plainness, there is a great deal of musical and liturgical history and theory surrounding these chants), and was one of the world's leading scholars on the subject. This recording of Ruhland and one of his choirs, the Choralschola of the Niederaltaicher Scholara, is a group of chants collected with an academic perspective in mind, but it's no less beautiful for it and may give new listeners some nice insights into the musicological subtleties of the style.
This lovely record presents one of the best collections of Gregorian Chants performed by female voices. The Sisters of L'Abbaye Notre-Dame de l'Annonciation, in Avignon, France, are a small and relatively young community (the convent, founded in the 1970s, is home to 30 nuns), but they live simply and in the traditional Benedictine fashion. All proceeds from this CD benefit their charitable works.
The Heiligenkreuz Abbey, in Southern Austria, is the oldest continuously-occupied Cistercian abbey in the world, and currently one of the largest and most influential, and the monks there have been singing plainchant for as long as they've existed. Praised by Pope Benedict XVI himself, they perform a particularly beautiful interpretation of plainchant, and this album (which came about after the monks auditioned via YouTube) sold millions of copies worldwide upon its initial release in 2008.
This collection, which was first recorded in 1959, is performed by the Benedictine Monks of the Abbey of St. Maurice & St. Maur, located in Clervaux, Luxembourg. It was recorded during an actual mass, so though it has the patina of a field recording, it is also a deeply holy and spiritually "present" example of Gregorian chant that most certainly has a home in any good collection.