Victoria set the hymn 'Ad preces nostras deitatis aures' (for Sundays in Lent) and there's a 3 part setting of V. 6 within that that's about 40 bars and integral. (There are nine vv, and all the even vv are polyphonic.) So I'd sing v. 1 (chant), v. 6 and then the doxology, v. 9.
You should also look at Marian and Eucharistic motets, as these are always appropriate for Mass. Lastly, you might consider discussing with the pastor the possibility of a devotion after Mass, for the Conclave.
Thanks for the shout-out, Chrism! Since you brought it up, my piece was just (2PM) broadcast on WAOB from Pittsburgh (rebroadcast is at 11 EDT and is Net-available.) Or go to my page off clevelandcomposers.org.
I just wrote a simple SAB piece for my choir on Friday. Might not be great art, but it's not terrible either! Very useful for church choirs of limited ability! PM me if you want a copy. It's a setting of the Hoc corpus / Holy Thursday Communion proper text in English translation.
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