Using several twelfth- and thirteenth-century sources, this study examines a selected number of Office antiphons, comparing their melodic variants for patterns of similarity and difference. The ancestry of a Sarum manuscript and - in another source - the survival of a pre-Conquest musical tradition in England are discernible in Office manuscripts examined as are affinities among French and English sources. Evidence from previous chant scholarship and certain medieval historical events shed light on the observations made in this study.