leeneia: I finally thought of the other good song from that collection- it's Personant Hodie.

...which has been translated as "Let the boys' cheerful noise" ("The Boys' Carol"), included (or translated?) by Elizabeth Poston in The Penguin Book of Christmas Carols.

Other popular carols from the Cantiones:

"Resonet in laudibus" (a 14th c. German song "Nunc angelorum") mostly known to us as "Joseph, lieber Joseph mein", "Let the voice of praise resound" or as Neale's free translation "Christ was born on Christmas Day"

"In vernali tempore", adapted by Neal as "O'er the hill and o'er the vale"

I suppose I should also mention "Corde natus ex Parentis" (De Eucharistia)--not among the facsimile set--which became "Of the Father's Heart Begotten". Neale also prepared a version of this under a slightly different title, which I've forgotten (his being inferior in quality, to my mind.)