As aural tuners, most of us learned to listen to the beat rates of the major thirds in the temperament octave, which is usually F3-F4. When I was a pup, my mentor set up a pendulum with a length of one meter, which therefore swings with a period of one second; and while watching the pendulum swing, I learned to recite "From Chicago to New York" so that the seven syllables filled the second... therefore the speed of the syllables was 7 per second, which was also the desired beat rate of the F3-A3 third. And so on with "From Mississippi to New York" and other such phrases.
The beat rates of these major thirds are formed by the simultaneous sounding of the fifth partial of the lower note with the fourth partial of the upper note. This page illustrates these frequencies, and the resulting beats, as they occur in a typical Steinway D as sampled with TuneLab.
The 4-second sound files are created using the shareware program Audacity, and emphasize the beating frequencies plus only a whiff of the fundamentals of the two piano tones comprising the major third.
|Major Third||5th partial
of the lower note
of the higher note