Beginning around A.D. 1000, musicians cultivated increasingly complex styles of polyphony. The earliest practical polyphony, from Winchester, Aquitaine and Paris, simply employed the prevailing style of plainsong notation. By the middle of the twelfth century, that notation accurately specified the pitch content of a melody, as I discuss in Chapter 2 and Interlude 1, and so the pitch content of the simultaneously sounding voices became secure. Rhythmic coordination in the Winchester polyphony of the eleventh century caused no problems because it proceeds in strict note-against-note style, and so each note in the organal voice corresponds to a single note in the liturgical chant. Aquitanian polyphony of the next century, however, often sets more notes in the upper voice than in the lower, and so debates ensue as to how to orient the two voices.