Aquitanian polyphony: Jubilemus, exultemus
Norton Recorded Anthology of Western Music, CD 1 Track 31
The early church, wanting to distinguish itself from uncouth neighbors, banned instrumental music almost entirely. And, so, vocal music enjoyed several hundred years of careful attention. When instrumental music becomes acceptable, as a reinforcement and extension of these vocal achievements, it serves sort of an apprenticeship. Listening to this admirable performance I am reminded how much instrumental music has benefited from this heritage.
For example, although the text and harmony of this piece are unmistakably ancient, the relationship of the two parts is familiar to modern ears. The tenor part, traveling at a slower speed than the upper, provides foundation and direction. With stability thus provided, the upper part has the proper setting to indulge in dissonance, expressiveness, and virtuosity.
What I like about this piece is the startling octave leap in the middle of the fourth line. Leading up to this leap the tenor part changes style in a way that is more engaged in the upper line. Then, after the leap, the tenor part returns to its initial polyphonic style. However, from here to the end the upper part increasingly explores this higher register. This reinforces the turn in the text on the line "He who today issued from Mary's womb...."