Ms 54 is a collection of miscellanea from the Cistercian monastery of Santa Maria de Santes Creus, near Tarragona.
On folio 132v (the final guard-page) a 2-voice organum was added, at the end of the 12th century, setting a trope of Benedicamus domino, in Aquitanian notation :
Reegi cuius sunt omina celebremus... In huius festi termino benedicamus domino