Polyphonic Chant at Opening of Papal Vespers?

[Dauphin]

I was deeply moved by the Sacred Polyphony which the choir sang before Wednesday’s Vespers and I was wondering if anyone knows the name of the composer or what the piece is called. I would very much like to know. I appreciate any help. Here’s the video; the polyphony begins right away:

mfile.akamai.com/18596/asf/atlanticvid.download.akamai.com/18594/wm.atlanticvideo/cc_pope/evening_prayer.asx

 

[brotherhrolf]

I looked at the Vatican’s website and it was not named. Stylistically, it sounds as if it was written during the Renaissance. It’s not one I recognize though.

 

[FrRJBoyd]

I’m on dial-up at the moment, so I can’t check the link, but I watched the Vespers live. They started with John Taverner’s Dum Transisset Sabbatum

cpdl.org/wiki/index.php/Dum_Transisset_Sabbatum_%28John_Taverner%29