The Athanasian Creed, Quicumque vult, is sung at Prime only once a year nowadays, and that is on Trinity Sunday. I've listened before to the podcasting monks do it here.
Last time I looked this up, they were doing the office of Prime recto tono, but when they got to the Creed, they switched to melody - don't know what was up with that.
Anyhow, you can follow along on p. 539 of the Antiphonale Monasticum (1934), available in .pdf here (you'll want part 2 of 3).
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