HEIRMOLOGION - (Irmologion)
- One of the basic liturgical books of the Orthodox Church, which contains the heirmoi for the entire year. There are two types of Heirmologion : a reader's version, which contains only texts, and a singer's version, in which the texts are supplied with musical notation. In the western Ukrainian and Byelorussian branches of the Orthodox Church the Heirmologion was a book that, in addition to heirmoi, contained the hymns of the Ordinary of Vespers, Matins, and Divine Liturgy, as well as hymns from the Octoechos and various feast-day hymns. The first printed edition of a notated Heirmologion in Russia -- the "Irmologiy notnago peniya," in square notation, was published in 1772.