Octoechus (Greek Ὀκτώηχος “eight-voice”, “voice”) is a liturgical book of the Orthodox Church, containing the rites of Vespers, Compline, Matins and Liturgy for the six weekday days of the week, and for Sundays, in addition - Little Vespers and midnight office. All these chants, according to the method of singing, are divided into eight voices (hence the name of the book) or tunes, each of which is used for one week. Named after belonging to the melodic system of osmoglasia. Translation into Russian: o. Ambrose Timroth