ORTHROS. -
In the Byzantine rite, this word designates the hour of the Divine Office corresponding to Matins in the Latin Office, including Lauds. This very lengthy hour, composed somewhat differently according to whether the Office is festal, Sunday, or weekday, may be divided into four principal parts.
1) The six Matins psalms (= hexapsalmos) 3, 37, 62, 87, 102, 142, recited by the reader while the priest says 12 prayers in a low voice; the Great Litany; several verses of Psalm 117 with troparia; 2) the variable psalmody, comprising three cathismata, or series of psalms; the last series is Psalm 118 or Psalms 134 and 135, called polyoleos; a brief hymn follows, anciently the reading of the Fathers, then gradual antiphons, and the Gospel (on feast days and Sundays); 3) Psalm 50 with a diaconal prayer, the nine scriptural canticles (omitted almost everywhere), and the Canon, composed of two, three, and generally eight odes; after the 6th ode, the reading of the Synaxarion; 4) the psalms of Lauds, 148, 149, and 150, the Great Doxology (= the «Gloria in excelsis» of the Roman liturgy together with the second part of the «Te Deum»), the Litany, and the dismissal.
From the fragmentary studies conducted on the history of O., it may be deduced, with some serious foundation, that the present O., virtually fixed by the 10th century, is the fusion of two originally separate hours, joined together before the 7th century: the Nocturn or Vigil and Matins ad galli cantum; the ancient Matins comprised Psalm 50, the hexapsalmos (or at least Psalm 62), the scriptural canticles (at least the «Magnificat»), the psalms of Lauds, and the Great Doxology.