The canon is the central hymn of one of the main church services, Matins1. And at Easter Matins, at which there are neither most of the usual psalms nor the reading of the Gospel, the canon is clearly the center of attention. If you serve strictly according to the rules, the lion's share of the time at Easter Matins will be devoted to the singing of the canon (and it is not small, it must also be performed with numerous repetitions), as well as to the reading of the 45th Word of St. Gregory the Theologian, on Holy Pascha2, a rather lengthy text.
The word of St. Gregory, written in the 4th century, and the Easter canon of St. John of Damascus, created approximately three and a half centuries later, are closely related. The canon contains several literal quotations from St. Gregory, so a true understanding of the canon is impossible without familiarity with the Easter words of the Great Cappadocian.
The Easter canon has a traditional structure: it has 8 cantos3, numbered from 1 to 9 (the 2nd canto is missing); each hymn opens with an irmos4, which should set the melody for the troparia5. In the 1st, 3rd, 5th, 6th and 9th cantos there are two troparions each, in the 4th, 7th and 8th there are three. The Theotokos6 are absent from the canon, but later hymnographers - Theophan and Joseph - added a set of Theotokos to the Easter canon; according to the modern charter, on the first day of Easter they are not sung, but on the following days both are performed (thus, after each song two Theotokos are added).