Octoechos

The Octoechos is a system of eight musical modes used to organize recurring cycles of Byzantine liturgical hymns. It also names the hymn collection arranged according to that system.

Byzantine chant: The monophonic liturgical singing tradition of the Eastern Orthodox Church and related churches. The Octoechos organizes a major body of hymns within this chant tradition.
Echos: A modal category in Byzantine chant that guides melodic movement and characteristic formulas. An echos is the basic unit counted in the Octoechos’ eight-mode scheme.
John of Damascus: An eighth-century theologian and hymnographer traditionally associated with organizing Byzantine chant. Tradition links him to the systematization of the Octoechos and its hymn repertory.
Orthros: The Byzantine morning service, corresponding broadly to the office of Matins. Octoechos hymns form a substantial part of the Sunday Orthros cycle.
Byzantine musical modes: The eight modal frameworks used in Byzantine chant to shape melody and performance. Each week of the Octoechos cycle is assigned one of these modes.
Authentic and plagal modes: Two related types of modal organization distinguished by range and melodic behavior. The eight Byzantine modes are grouped into four authentic and four plagal modes.
Romanos the Melodist: A sixth-century Byzantine hymnographer renowned for composing kontakia. His hymns belong to the earlier tradition from which later Byzantine cycles drew.
Vespers: An evening liturgical service marking the beginning of the Byzantine church day. Its weekly hymns follow the mode assigned by the Octoechos cycle.
Byzantine liturgical calendar: The annual sequence of feasts, fasts, and commemorations observed in Byzantine-rite churches. Its weekly cycle coordinates with the calendar’s recurring services and feast days.
Psalmody: The practice of singing or reciting biblical psalms in worship. Psalm verses provide the framework around which many Octoechos hymns are sung.

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