Music is created in all known human cultures and is an integral part of the daily lives of many people worldwide. Historically, one of the most remarkable findings concerning music has been the discovery of primitive flute-like musical instruments made from animal bones, dating from 10,000 to 40,000 years ago (Figure 2.1). Although the actual musicality of such instruments is uncertain, the number of holes in the shaft of the bone indicates that three or four distinct tones were produced by our early caveman ancestors.

It therefore seems certain that melodies have been played in human communities for many millennia. The simultaneous use of two or more such instruments would allow for the production of consonant and dissonant intervals, but concrete indications of the development of polyphonic musical sounds are not found until ancient Greek discussions of the psychological character of pitch intervals. And it is not until the development of written musical notation around 1000 AD (Figure 2.2) that two different pitches were an explicit (written) part of musical culture. From that time onward, the gradually increasing complexity of pitch combinations is well documented in the historical record, but, from a modern perspective, what remains surprising is that the use of three simultaneous pitches emerged only quite recently (~1300 AD).