source file: m1483.txt Date: Fri, 24 Jul 1998 07:37:05 -0500 Subject: Re: Overtones and Tone Color From: Gary Morrison > Are overtones different frequencies > produced by different aspects of whatever materials are producing the sound? The materials vibrating a significant factor, but the most important factor is the shapes and available kinds of movements possible in that configuration. The most important thing about a string, for example, is that its diameter is only a tiny fraction of its length, that it is anchored firmly at both fret and bridge ends, and that it is made of a flexible material. This is what allows it to vibrate at very nearly precisely-harmonic frequencies. What makes those frequencies not completely harmonic are the departures from this idealized model of a string, such as the fact that high piano strings' are so short and thick, and under such high tension, that they are no longer a close approximation to being arbitrarily flexible and infinitely longer than their diameter. As another example, the most acoustically-significant difference between a clarinet and a saxophone is that the saxophone's bore is conical, meaning that the diameter of the tube is much narrower at the mouthpiece end than at the bell end. Except for the bell at the end of the horn (which has a lot less acoustical significance than it would initially seem), the clarinet's bore is much closer to cylindrical (i.e., nearly equal diameter throughout). The combination of a cylindrical bore and a reed produces stronger odd-numbered harmonics than even ones, whereas, a saxophone (as well as other conical-bored instruments like the oboe, bassoon, or most brasses), have about the same prominence of even and odd harmonics. Now in the case of wind instruments, it's very critical to understand what the "materials" are. What vibrates in a wind instrument is the air inside the tube. The walls of the instrument itself vibrate only slightly, except in a mere handful of specific cases (quadruple-forte, unstopped F.horn, for example). That is obviously completely the opposite for a stringed instrument - the soundboard is the entire means of transferring the sound generated by the strings to the air, so the soundboard imparts its vibrational qualities to the sound of the instrument. That is NOT to say that the material a wind instrument is made of has absolutely NO effect upon its timbre, but that is a much less significant factor than its forcing means (e.g., reed, edge, lip-buzzing) and its bore geometry. No matter what material you make a flute out of, it's always going to sound more like a traditional flute than like a bassoon.