- A system of classifying liturgical poetry and melodies into eight categories, known as Tones. Derived originally from the Palestinian practice of singing Paschal hymns to a different melody (Tone) on each of the eight days of the feast, the Eight Tones came to be applied to eight week-long cycles of hymns. As early as the 6th c., these hymns were compiled into a book known as the Octoechos, which was systematized and edited in the 8th century by St. John of Damascus. While in the Greek and Roman Churches the system of Eight Tones is based largely upon differences between modes or scales, in the Russian Church the Tones are differentiated by groupings of characteristic melodic formulae (popevki). The system of Eight Tones governs the hymns of the Proper from the Octoechos, Festal Menaion, and the Triodia -- stichera, troparia, kontakia, kanons, prokeimena, gradual antiphons, and kathisma hymns -- as well as certain hymns of the Ordinary, e.g., "Lord, I Call" and "Gladsome Light" at Vespers, and "It Is Truly Fitting" and the "Alleluia" at the Divine Liturgy, which have been set to the Eight Tones of znamenny and other chants.