For others, recitation of all three is recommended and, in order to preserve the tradition of praying during the day's work, those who have the duty to celebrate the Liturgy of the Hours are obliged to say at least one.
They begin with the versicle Deus in adiutorium meum intende and its response, followed by Gloria Patri and (except in Lent) Alleluia.
At the Little Hours, the majority of the Office is read (actually a simple recitative—never just said with the normal speaking voice) by the reader alone, with very few variable parts.
On weekdays, in addition to the normal three Psalms, a kathisma from the psalter is read, the choir chants special Lenten hymns in place of the Troparion and Kontakion of the day, and the Sixth Hour has added to it a special Troparion (called the "Troparion of the Prophecy"), Prokeimena, and a reading from the Old Testament (Joel and Zechariah during Cheesefare Week, Isaiah during the Forty Days of Great Lent, Ezekiel during Holy Week).
[18] (In monasteries, it is traditional to add a reading from the Ladder of Divine Ascent at the Third, Sixth, and Ninth Hours.
During Holy Week, on Monday, Tuesday and Wednesday, the services are similar to those during Great Lent (including the reading of Kathismata), except that instead of the normal Lenten hymns which replace the Kontakion, the Kontakion of the day (i.e., that day of Holy Week) is chanted.
This service takes its name from the fact that it used to be officially attended by the Emperor and his court at Hagia Sophia in Constantinople.
The holy doors and curtain are open for most of the service, and the gospel book is placed on an analogion (lectern) in the center of the temple.
At each of the Hours, one of the three fixed Psalms is replaced by a Psalm that is significant to the Feast being celebrated; the Troparion and Kontakion of the day are replaced by numerous hymns chanted by the choir; and each Hour has an Old Testament reading, a Prokeimenon, and an Epistle and Gospel.
On the Sunday of Pascha (Easter) itself, the priest vests fully, as for Divine Liturgy; on the other days of Bright week, he wears Epitrachelion, Epimanikia and Phelonion.