Brown, Barnaby

Celtic chant is the monophonic, liturgical plainchant associated with the Celtic rite practiced by early medieval Christian communities in Celtic Britain, Gaelic Ireland, and Brittany. Closely related to other Western chant families yet distinct from the Roman-Gregorian tradition that later prevailed, it accompanied the Mass and Office in monastic and ecclesiastical contexts. No authentic notated melodies of Celtic chant survive; consequently, its musical profile is inferred from liturgical books, textual parallels, and comparative study with sibling chant traditions. By the 12th century, the Roman rite (and its Gregorian chant) had supplanted the Celtic rite, leaving Celtic chant as an extinct but historically significant strand of early Western liturgical song.

Plainchant (cantus planus) is the monophonic, unaccompanied chant of the Western Christian liturgy. Sung in Latin (with occasional Greek), it uses modal scales rather than major–minor tonality and unfolds in flexible, speech-like rhythms shaped by the sacred text. Melodically, plainchant ranges from simple syllabic formulas for reciting psalms to ornate melismatic lines for processional and festal moments. It is performed in unison by a schola or congregation, often organized antiphonally or responsorially across the liturgical actions of the Mass and the Divine Office. Its austere sonority, modal color, and text-centered phrasing give it a contemplative, timeless quality.