The liturgical book called Octoechos (from the Greek: ἡ Ὀκτώηχος Greek pronunciation: [okˈtoixos]; from ὀκτώ "eight" and ἦχος "sound, mode" called echos; Slavonic: Осмѡгласникъ, Osmoglasnik from о́смь "eight" and гласъ "voice, sound") contains a repertoire of hymns ordered in eight parts according to the eight echoi (tones or modes). Originally created as a hymn book with musical notation in the Stoudios monastery during the 9th century, it is still used in many rites of Eastern Christianity. The hymn book has something in common with the book tonary of the Western Church. Both contained the melodic models of the octoechos system, but the tonary served simply for a modal classification, while the book octoechos is as well organized as a certain temporal of several eight week periods and th