ABSTRACT
The Magnus liber organi de gradali et antiphonario is a collection of settings of responsorial chants of the Office and the Mass in the form of organum duplum. The word "clausula," however, continued to be used in its restricted sense of a rhythmic cadence, in treatises that dealt with the form of artistic prose known as the cursus. Of the various meanings of "clausula" sketched above, it seems more than likely that Anonymous IV must have had the theory of rhythmic poetry in mind when he spoke of the "clausulae vel puncta." A study of the relationship of the other pieces in the third series of substitute clausulae to their parent compositions will produce results comparable to these found in the examination of the Alleluya: Nativitas. In a truly monumental footnote to his discussion of the abbreviation of the Magnus liber, Mr. Dittmer reconstructs a "lost" treatise by Leo or Leoninus.
