Just a lovely song that I first heard at my parish church during Communion, beautifully performed by our organist and soloists from the Gregorian chant choir.

The words are a brief but powerful medieval Eucharistic hymn, one of my favorites.  From Wikipedia:

Ave verum Corpus
natum de Maria Virgine,
vere passum, immolatum
in cruce pro homine,
cuius latus perforatum
unda fluxit et sanguine,
esto nobis praegustatum
in mortis examine.

Hail, true Body,
Born of the Virgin Mary,
Truly suffered, immolated
On the Cross for man,
Whose pierced side
Flowed with water and blood,
Let it be for us a foretaste [of Heaven]
In the trial of death.

This duet setting was written by the Welsh composer Karl Jenkins in 2004, for the Welsh baritone Bryn Terfel.

Here is Terfel singing it with the English bariton Simon Keenlyside:

And here is a live performance with Terfel and the Welsh mezzo-soprano, Katherine Jenkins: