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What Is Music? 43monic overtones lack the clear sense of pitch that we associate with harmonicinstruments, and the cortical basis for this may relate to a lack ofsynchronous neural firing. But they still do have a sense of pitch, and wehear this most clearly when we can play inharmonic notes in succession.Although you may not be able to hum along with the sound of a singlenote played on a woodblock or a chime, we can play a recognizablemelody on a set of woodblocks or chimes because our brain focuses onthe changes in the overtones from one to another. This is essentiallywhat is happening when we hear people playing a song on their cheeks.A flute, a violin, a trumpet, and a piano can all play the same tone—that is, you can write a note on a musical score and each instrument willplay a tone with an identical fundamental frequency, and we will (tendto) hear an identical pitch. But these instruments all sound very differentfrom one another.This difference is timbre (pronounced TAM-ber), and it is the mostimportant and ecologically relevant feature of auditory events. The timbreof a sound is the principal feature that distinguishes the growl of alion from the purr of a cat, the crack of thunder from the crash of oceanwaves, the voice of a friend from that of a bill collector one is trying tododge. Timbral discrimination is so acute in humans that most of us canrecognize hundreds of different voices. We can even tell whether someoneclose to us—our mother, our spouse—is happy or sad, healthy orcoming down with a cold, based on the timbre of that voice.Timbre is a consequence of the overtones. Different materials havedifferent densities. A piece of metal will tend to sink to the bottom of apond; an identically sized and shaped piece of wood will float. Partly dueto density, and partly due to size and shape, different objects also makedifferent noises when you strike them with your hand, or gently tap themwith a hammer. Imagine the sound that you’d hear if you tap a hammer(gently, please!) against a guitar—a hollow, wooden plunk sound. Or ifyou tap a piece of metal, like a saxophone—a tinny plink. When you tapthese objects, the energy from the hammer causes the molecules withinthem to vibrate, to dance at several different frequencies, frequenciesdetermined by the material the object is made out of, its size, and its