The final section of the 15th-century Dartmouth Magnificat (anon), from the CD Plainsong and Polyphony by Voces, directed by Martyn Warren.
I regard this recording as work in progress - there are so many questions about performance practice, not least pitch. We sing it close to 'written' pitch rather than transposing down a fourth or fifth in recognition of the high clefs. The result is much brighter than it would otherwise be, but puts strain on the treble line. Next time a compromise between the two, perhaps.