The Pascha Nostrum is a beautiful set of anthems that Anglican tradition uses at Easter. It is built upon three scriptural references: 1 Corinthians 5:7-8, Romans 6:9-11, and 1 Corinthians 15:20-22, each bookended with an Alleluia for good measure.
It has always been in Anglican Prayer Books, but its location has changed in modern practice. Traditionally, it was placed among the Propers (the Collects and Lessons), for Easter Day; in modern books it is placed in the Morning Prayer liturgy. It’s interesting to note how the rubrics for this canticle have changed over the years.
At Morning Prayer, instead of the Psalm: O Come, let us, &c. these Anthems shall be sung or said.
At Morning Prayer, instead of the Venite, the following shall be said, and may be said throughout the Octave.
During the first week of Easter, the Pascha Nostrum, without antiphons, is used in place of the Invitatory Psalm, and it may be used throughout Eastertide.
What stays the same? its function. This Canticle is always used in place of the Venite in Morning Prayer. What has changed? its duration of use. The implication back in 1662 is that this canticle (or set of anthems) only gets used on Easter Day. By 1928 in the US, it was authorized throughout the octave – that is, the first eight days of Eastertide. Now, it is appointed (not merely authorized) throughout Easter Week and authorized for the rest of Eastertide. With this increased anticipated use, it’s no wonder that modern prayer books have opted for printing this canticle directly in the Morning Prayer liturgy, so it’s more accessible!
There is also a custom in some places of using the Pascha Nostrum in place of the Gloria in excelsis Deo near the beginning of the Communion service, under the modern rubrics that allow other hymns of praise to take its place. Especially in church cultures where nobody is really praying the Daily Office, this can be a great way of introducing elements of the Office liturgies to the congregation. Such points of contact and familiarity will prove helpful when trying to make that move toward teaching people to pray the Office.