Franco of Cologne on the rhythm of organum purum

Thanks in part to a fine translation by Oliver Strunk, theArs cantus mensurabilisof Franco of Cologne is a treatise we all think we know. It is perhaps for this reason that Franco's treatise has been all but ignored in most of the recent discussions of the rhythm of Notre Dame organum. The one noteworthy exception to this is Fritz Reckow's discussion of organum purum in his dissertation on Anonymousivand in his various articles on organum and related topics in theHandwörterbuch der musikalischen Terminologie, in the SchradeGedenkschrift, and elsewhere. But for Reckow, and presumably for most other scholars as well, Franco's description of organum is strongly coloured by his theories of mensuration, appearing to place even organum purum under the heading of ‘mensurable music’. This in turn seems to distance Franco from the earliest layer of organum composition at Notre Dame, rendering his ideas of little value in arriving at an interpretation of the rhythmic character of this music.