Irmologion

These canons of nine, eight, four or three odes are to be chanted during the morning service (Orthros). The name irmologion derives from heirmos (ὁ εἱρμός), which means 'link'. The irmos is a melodic model which preceded the composition of the odes. According to the etymology, the book 'collects' (λογεύω logeuō) the irmoi. An important portion of Matins and other services in the Orthodox Church is the canon, a long liturgical poem divided into nine strophes with a sophisticated meter called ode. Each ode and its prosodic meter is made according to a certain irmos, and concerning its celebration during Orthros it is followed by troparia called akrosticha. Sometimes certain longer irmoi are sung which are called katabasiai because of their descending melos. The troparia sung with the canon are performed out of a textbook (Reader, Menaion) according to avtomela, but the irmoi and katabasiae are chanted by the choir according to the model of the irmoi.