Just had a friend give me an article from Scientific American Oct. 1973 page 94, on Auditory Beats in the Brain. It concerns itself with binaural beats created in the brain when tones of different frequency are presented separately to each ear. Interesting article, BUT: "The tuning of pianos is another precess that depends on beats. Typically the piano tuner will first listen for the beats produced by a tuning fork of 440 hertz and the A above middle C, and tighten or loosen the A wire until the beats slow to zero. He then strikes the A key and the D key below it and tunes the latter wire until 10 beats per second are heard. That frequency is produced by the interaction of the A string's second harmonic, or second multiple (2x440=880), and the D string's third harmonic (3x290=870). In this fashion, key by key, the piano is tuned; in theory it could be done even by someone who is tone-deaf." Larry Messerly, RPT Prescott/Phoenix (too much time on my hands, I don't get to tune until noon today.)
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