Precious few records of Old Roman Chant remain, many having being intentionally destroyed by the Franciscans intent on imposing the Romano-Frankish modes. Ensemble Organum have attempted to reconstruct, with their usual meticulous scholarship, what it might have sounded like. The result is mindblowing, and makes one weep for what treasures of beautiful music must have been lost forever with the triumph of the somewhat blander, "dumbed-down" Gregorian forms. This recreation, as the sleeve notes say, "brings alive the missing link between Byzantine, Coptic, Armenian and Syrian Chant, and Arab and Western music". Fabulous stuff.
In my modest opinion this is an amazing record.