sentences:  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 the word itself means the repertoire of hymns sung during the celebrations of the Sunday Office.Kathismata, odes or kontakia are set in a strict meter—a rhythm within a fixed number of verses as a strophe, a fixed number of syllables and accents as a verse.