Q: What is a Psalter?

Q: What is a Psalter?

A: The Psalter is a liturgical book which contains the 150 Psalms of King David from the Old Testament. The Psalms are arranged or grouped into twenty sections called Kathismata – a Greek word meaning "to sit," since the people normally sit down while they are being chanted. These Kathisma are also laid out in such a way so that the Psalter can be read in its entirety over the course of one week at the daily services of matins and vespers. During the weeks of Great Lent, however, the Psalter is read through twice.
Besides containing the Psalms, some editions of the Psalter include additional prayers – such as prayers for the departed (because it is the Church's tradition to read the Psalms over the deceased) and the Nine Biblical Canticles:

Canticle One — The 1st Song of Moses (Exodus 15:1-19)
Canticle Two — The 2nd Song of Moses (Deut. 32:1-43)
Canticle Three — The Prayer of Hannah (1 Samuel 2:1-10)
Canticle Four — The Prayer of Habakkuk (Habakkuk 3:1-19)
Canticle Five — The Prayer of Isaiah (Isaiah 26:9-20)
Canticle Six — The Prayer of Jonah (Jonah 2:2-9)
Canticle Seven — The Prayer of the Three Holy Children (Daniel 3:26-56)
Canticle Eight — The Song of the Three Holy Children (Daniel 3:57-88)
Canticle Nine — The Song of the Theotokos: "Magnificat" (Luke 1:46-55)

Fr. John