The chants from the second link are from the album Plain-Chant de la Cathedrale d'Auxerre by Ensemble Organum (excellent group! buy their stuff!).
I've plugged their work several times on the board. Yes, Marcel Peres is a very accomplished director and researcher of sacred music and its history, and with colleagues such as Lycourgos Angelopoulos, and Sr. Marie Keyrouz (invited to contribute to his recording of Ambrosian chant), high-calibre musical results are not unusual.
Very beautiful, even if they are probably infringing copyright. Good luck finding the album, though, as it's long out of print.
You might become lucky. Look for copies by Musique d'Abord
that seem to be distributing some of Organum Ensemble's work (such as Chants de l'Eglise de Rome: Periode Byzantine
which I went through much trouble trying to obtain) at low prices.
In IC XC