very nice, i am not sure why you titled this 'Lamb of God',though,since this has nothing to do with the' Agnus Dei' and are instead mix of Psalms with their Antiphons, ( and part of a Graduale? in the middle)from a Marian Feast..,sounds like its from the St. Benedict's Monastery in São Paulo (Brazil)..thank you for uploading!!!...
PAX