A Dictionary of Music and Musicians/Prime
PRIME (Lat. Prima; Hora prima. Officium (vel Oratio) ad Horam primam). The first of the 'Lesser Hours' in the Roman Breviary.
The Office of Prime consists of the Versicle and Response, 'Deus in adjutorium'; a Hymn, 'Te lucis orto sidere,' which never changes; and three Psalms, sung under a single Antiphon. These are followed, on Sundays, by the Hymn 'Quicunque vult,' commonly called the Creed of S. Athanasius. On other occasions the Antiphon is immediately succeeded by the Capitulum and Responsorium breve. The disposition of the next division of the Office, including the Preces and the Martyrologium for the day, depends entirely upon the rank of the Festival on which it is sung. Certain Prayers are said, next in order; and the whole concludes with the Lectio brevis and the Benediction.
The Plain Chaunt Music for Prime will be found in the 'Antiphonarium Romanum' and the 'Directorium Chori.'