?Scientific American?

[Larry J. Messerly]

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.)