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These are the stages of polyphony. (stage number, name, and description)
What is Stage 1: early polyphony, parallel and oblique motion. Stage 2: free organum, parallel, oblique, similar, and contrary motion. Stage 3: Aquitanian polyphony, Aquitaine, France, florid organum and discant. Stage 4: Notre Dame polyphony, essentially Aquitanian polyphony plus rhythmic modes notated in ligatures?