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Before western music was written as notes on paper it was played through the lyre and aulos by ancient Greek musicians. Although you could never hear the same song twice, their improvisations were connected by the modes through which they improvised. The twelve note scale had not yet been organized into keys, but it had divided itself into a series of textures which are still used in improvisation today. At first glance it would seem that later church music, with key signatures and harmonies, was much more complex than ancient Greek music, but Greek musicians had learned through experience that specific series of notes had their own moods and feelings. That is something that cannot merely be seen or taught through polyphony, but was still heard and understood by ancient philosophers, notably Aristotle, and every jazz saxophonist today worth his weight. The Greeks believed that music should portray specific emotions and that it could evoke those emotions within its listeners. Musicians did this without any body of written knowledge to tap in to but through solo improvisation.