We can be tempted to think of Gregorian chant as a fixed canon, handed down since time immemorial, unchanging like the Faith. But it is good to remember that over history chant has been subject to much change, whether in its composition, liturgical use or performance. For example, when a new feast arises in the Church, where do the chants to celebrate it come from? They can be taken from other feasts, newly composed, or something in between: putting new words to an ancient tune or combining bits of different tunes to make a new one.
A good example of this is the Feast of the Sacred Heart: there have been four different sets of Mass chants in use since it was first celebrated in 1672, and it was not until 1929 that the set of chants we use today was finalised.
St John Eudes, who composed the first Mass of the Sacred Heart in 1670, used several methods for making his Mass chants, adapting the common Introit “Gaudeamus”, borrowing his Alleluia “Paratum” from a Sunday Mass and creating his own unusual non-Biblical Communion text.
In 1929, the creators of the latest Mass put their chants together similarly, working with pre-existing melodies to make something new but rooted in tradition. In doing this they created links between the new chants and pre-existing ones which can resonate with the attentive singer or congregant.
Particularly striking is the 1929 Communion chant. The text is:
Unus militum lancea latus ejus aperuit,
Et continuo exivit sanguis et aqua.
One soldier pierced his side with a lance,
And immediately there came out blood and water.
This is well-chosen for the Feast, and perfect for Communion for obvious reasons. But the melody for the chant is also an inspired choice: it was adapted from an ancient Communion chant, “Qui biberit aquam”, which recounts the tale of Jesus and the Samaritan woman, in which he offers living water, springing up to eternal life.
“Qui biberit aquam” was not used in the Extraordinary Form, so the connection would have been hidden before 1970, but in the Ordinary Form it can be used for the Third Sunday in Lent (Year A). When it is, and when the chants for the Sacred Heart are also sung, the music brings the two texts together – the fount of Living Water in our heart and the water pouring from the side of Jesus on the Cross.
As both are communion chants, we are reminded as we process to the sanctuary that it is from the Heart of Jesus, pierced on the Cross and joined to us in Holy Communion, that gives and renews within us the fount of living water.