Here is the Gregorian Introit for the Fifth Sunday of Easter. This is one of my favourites, and a great one for all singers (and the name of our choir here!)
“Sing to the Lord a new song, alleluia; for the Lord has accomplished wondrous deeds, alleluia; he has revealed his justice in the sight of the Gentiles, alleluia, alleluia. V. His right hand and his holy arm have given him victory.”
(Thanks to CCWatershed and their collection of practice videos for the Propers!)