This article is about the Byzantine musical system of eight modes. For the book of liturgical texts set to those modes, see Octoechos (liturgy).

Oktōēchos (here transcribed "Octoechos"; Greek: ὁ Ὀκτώηχος [ modern Greek: oktoˈixos, old Greek: oktɔːˈɛːkʰos ], from ὀκτώ "eight" + ἦχος "sound, mode" called echos; Old Church Slavonic: Осмогласие, Osmoglasie from о́смь "eight" and гласъ, Glagolitic: ⰳⰾⰰⱄⱏ, "voice, sound") is the name of the eight-mode system used for the composition of religious chant in Byzantine, Syrian, Coptic, Armenian, Latin and Slavic churches since the Middle Ages. In a modified form the octoechos is still regarded as the foundation of the tradition of monodic Orthodox chant today.


The names ascribed to the eight tones differ in translations into Church Slavonic. Тhe Slavonic system counted the plagioi echoi as Glas 5, 6, 7, and 8. For reference, these differences are shown here together with the Ancient Greek names of the octave species according to the Hagiopolites[1] and to the chant treatises and tonaries of Carolingian theorists. Please note that 15th-century composers like Manuel Chrysaphes, Lampadarios at the Court of Palaiologan Constantinople, exchanged the Phrygian with the Lydian. The Armenian names and their temporal cycles are represented in the article about the hymn books octoechos and parakletike.

Byzantine octoechos Church Slavonic osmoglasie Octave species Carolingian octo toni
First (ἦχος πρῶτος) First (гласъ а.) Dorian Tonus primus / Authentus protus
Second (ἦχος δεύτερος) Second (гласъ в.) Phrygian Tonus tertius / Authentus deuterus
Third (ἦχος τρίτος) Third (гласъ г.) Lydian Tonus quintus / Authentus tritus
Fourth (ἦχος τέταρτος) Fourth (гласъ д.) Mixolydian Tonus septimus / Authentus tetrardus
Plagal of the First (ἦχος πλάγιος τοῦ πρώτου) Fifth (гласъ є.) Hypodorian Tonus secundus / Plagis proti
Plagal of the Second (ἦχος πλάγιος τοῦ δευτέρου) Sixth (гласъ ѕ.) Hypophrygian Tonus quartus / Plagis deuteri
Grave (ἦχος βαρύς) Seventh (гласъ з.) Hypolydian Tonus sextus / Plagis triti
Plagal of the Fourth (ἦχος πλάγιος τοῦ τετάρτου) Eighth (гласъ и.) Hypomixolydian Tonus octavus / Plagis tetrardi

Note that southern Slavs use the Byzantine musical system and, nonetheless, use the variant numbering that is always found in Church Slavonic texts.[2]


According to three main periods, which divides the history of the eight-mode system, the former article has been split chronologically:

Octoechos Period Reference
Hagiopolitan Octoechos 6th-13th century Pseudo-John of Damascus[1]
Papadic Octoechos 13th-18th century John Glykys, John Koukouzeles
Neobyzantine Octoechos 18th-21st century Chrysanthos of Madytos


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