The readings for this Sunday are:
Psalm 80:1-8, 18-20
1 Corinthians 1:3-9
Serious stuff. Repentance is a theme in Isaiah and the Psalm; 1 Corinthians is more encouraging, and the Gospel reading is about keeping awake.
If you’re of a Marian bent you could use the Alma Redemptoris Mater, which is the Marian antiphon used from Advent to Candlemas. There’s a setting by Isabella Leonarda available on CPDL; here’s a Youtube recording of it sung by women, rather than the SATB:
[external link: Alma Redemptoris Mater by Isabelle Leonarda, on Youtube]
If Advent carol services and processions are more your thing, you could sing Stephanie Martin’s Legend of the Bird, a carol in the form of a conversation with a robin about the return of Christ. It’s available to order from Cypress Choral Music, and here it is on Soundcloud:
[external link: Legend of the Bird by Stephanie Martin, on Soundcloud]
[external link: Advent by Kathryn Rose, on Youtube]
There are also arrangements by women of various traditional Advent tunes; these are in some ways beyond the remit of Cecilia’s List, but the two that spring to mind are O Come O Come Emmanuel arranged by Sheena Phillips, and Es kommt ein Schiff, geladen by Sigrid Schultz-Kokerbeck. I’m intrigued by the text for the latter — there’s more information at good old Wikipedia but no English translation there, and my German is pretty shaky; however, I did find this blog post from 2013 with an English translation.