Authentic frets

Authentic frets (from late Lat . Authenticus - authentic, authentic ) is a term by which in music of the Middle Ages four main, or main, church frets were understood, with finalises d, e, f, g . Authentic modes were called numerals (Greek), respectively, protus, deuterus, tritus and tetrardus. Four other frets that fit a quart below the authentic ones — A, H, c, d — are considered derivatives and are called plagals. None of these eight modes had the same importance as the major and minor modes (see Modality , Tonality ). The term is first found in the tonarias of Saint-Ricier and Metz , in the treatise “Musica dicsiplina” by Aurelianus of Reome and in other sources of the Carolingian Renaissance (last quarter of the 8th – 9th centuries).