OCTOECHOS. — Liturgical book of the Byzantine rite, containing the proper parts of the Divine Office for a series of eight consecutive weeks, according to the progression of the eight musical tones; it is used throughout the liturgical year, except during Lent, the Easter season, and the major feasts. No study exists on the history of the O.; the arrangement of the book is attributed to St. Giovanni Damasceno, but without sufficient foundation. It is perhaps the liturgical book richest
in doctrinal content. Editio princeps, in Greek, Venice 1525.
BIBL.: Krumbacher, p. 674; K. Weber, Die serbischkirchen-slavische Oktoechos-Handschrift Cod. slav. 46 der Wiener Nationalbibliothek, Vienna s. d. [1936], with a brief, good general introduction preceding a critical survey of the studies carried out on the Slavic O.; H. J. W. Tillyard, The Hymns of the Octoechos, Copenhagen 1940, provides the medieval chant in modern transcription.