All Orthodox liturgical books can be divided into sacred liturgical books (Gospel and Apostle) and church liturgical books. The most used book from the second group is Oktoih.
It is impossible to imagine the modern Orthodox worship of the daily circle without the use of Oktoikh - a book that publishes prayers of the main weekly and daily services of the eight voices (tunes). Due to this content, Oktoikh is otherwise referred to as the Ottoman.
Oktoih is issued in two parts: the first volume contains liturgical texts from the Vespers, Laucher, Midnight, Matins and Liturgy from the first to fourth voices inclusive; the second volume implies the presence of the same divine services of the fifth to eighth voices.
Oktoikh is used in worship daily for most of the year. The exceptions are periods of great holidays, for example, Easter celebrations. The greatest application of this book relates to the services of Vespers and Matins, which are sent to all Orthodox churches. It is in Oktoikha that there are stichera, saddles and canons, chanted or deducted during worship.
Liturgists attribute the compilation of Oktoikh to the 7th century. It is known that later this book was edited and supplemented by the great saints of the Christian Church. It is worth noting especially the Monk John of Damascus, who made the greatest contribution to the development of Oktoikh an indispensable book for worship (VIII century).
In each part of Oktoikh there are applications in which important prayers of individual divine services are published. For example, weekly lights (by the days of the week), 12 Gospel verses of Sunday matins, as well as the same number of Sunday exostals and Mother of God.
At present, one can find in addition to the two volumes the music of Oktoih. It contains notes of the main chants of the eight voices used in church life.
