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What Is Music? 45able from the timbral fingerprint for a violin, piano, or even the humanvoice. To the trained ear, and to most musicians, there even exist differencesamong trumpets—all trumpets don’t sound alike, nor do all pianosor all accordions. (Well, to me all accordions sound alike, and the sweetest,most enjoyable sound I can imagine is the sound they would makeburning in a giant bonfire.) What distinguishes one particular piano fromanother is that their overtone profiles will differ slightly from each other,but not, of course, as much as they will differ from the profile for a harpsichord,organ, or tuba. Master musicians can hear the difference betweena Stradivarius violin and a Guarneri within one or two notes. I canhear the difference between my 1956 Martin 000-18 acoustic guitar, my1973 Martin D-18, and my 1996 Collings D2H very clearly; they sound likedifferent instruments, even though they are all acoustic guitars; I wouldnever confuse one with another. That is timbre.Natural instruments—that is, acoustic instruments made out of realworldmaterials such as metal and wood—tend to produce energy at severalfrequencies at once because of the way the internal structure oftheir molecules vibrates. Suppose that I invent an instrument that, unlikeany natural instruments we know of, produces energy at one, and onlyone, frequency. Let’s call this hypothetical instrument a generator (becauseit can generate tones of specific frequencies). If I line up a bunchof generators, I could set each one of them to play a specific frequencycorresponding to the overtone series for a particular instrument playinga particular tone. I could have a bank of these generators making soundsat 110, 220, 330, 440, 550, and 660 Hz, which would give the listener theimpression of a 110 Hz tone played by a musical instrument. Furthermore,I could control the amplitude of each of my generators and makeeach of the tones play at a particular loudness, corresponding to theovertone profile of a natural musical instrument. If I did that, the resultingbank of generators would approximate the sound of a clarinet, orflute, or any other instrument I was trying to emulate.Additive synthesis such as the above approach achieves a syntheticversion of a musical-instrument timbre by adding together elementalsonic components of the sound. Many pipe organs, such as those found