Continuing on from the last post, in the post-Guidonian period, starting around the second half of the 11th century, organum began changing.
Beginning with Ad organum faciendum, we see that organum at the fifth and organum at the fourth were no longer distinguished. Instead, the treatise offers one organum in which fourths and fifths are intermixed. Position of the vox organalis was now above and not below the vox principalis, and the voice-crossing appears more often, unlike the earlier, Guidonian practice when it could only appear if the principal voice goes below the lower pitch limit – what was called organum suspendum. In terms of the melodic shape, not only were parallel and oblique motions combined, without the drones for the latter, but we also see contrary motion being introduced. Because of this mixture of melodic movements, this type of organum may be termed free organum.
While the appearance of the oblique organum was justified by the avoidance of tritones which could occur in the parallel motion of the fourths, the principle behind free organum doesn’t involve the symphoniae (term for consonants, see the previous post). Instead, it is guided by the Guidonian doctrine called affinitas vocum. (Fig. 1)
Fig. 1. The illustration of Guido’s affinitas vocum Continue reading “Project 9 Examples Research, Part 2: Descant, Post-Guidonian Organum, and the Rise of Modal Rhythm”