Agnus Dei

O Lamb of God,
who takest away the sins of the world,
have mercy on us.

The ‘Agnus Dei’ is sung directly before Communion is taken, focusing our attention on Jesus Christ as the one who gave his body and blood to atone for our sin. It is almost always quiet, and its gentle repetitions encourage meditation.
 
The opening melody that the choir sings (after the organ gives them almost every note except for the one they have to start singing!) is based on a little tune in my Piano Sonata that I never expected to use in this way.

Here’s its original context, right at the beginning of the ‘At Church’ movement, sounding lively and a little mischievous…

And here’s how I’ve transformed it to use in the Agnus Dei…

I turn the phrase downwards at the end, to paint the sadness of “the sins of the world”, and I leave the choir hanging for a moment without the organ… Then comes the peaceful supplication, “have mercy on us.”
 
The words here deliberately echo the opening ‘Kyrie’, asking for mercy. So I thought it made sense to do this with the music as well. I put the nine-bar phrasing of the ‘Kyrie’ chant in the organ, underneath the simple words of the choir…

After that, the music simply follows repetitions of the text, but changing key to arrive at a particularly expressive chord at the start of the last stanza. From there I had to find a quick but gentle way back to the home key (C) to ensure it sounds like the prayer is answered!