Why two almost-equal notes make a wobble: beats and the piano tuner's trick
30seconds
Play two almost-equal notes together and you hear one pitch that swells and fades. Those swells are beats, and their rate is simply the difference in frequency: 440 Hz against 442 Hz gives 2 beats a second.
Slide the second note, watch the two waves add up, and hear the pulse slow to nothing as the pitches match. Then tune a hidden string by eye and ear, the way a piano tuner turns a tiny pitch gap into a rhythm you can count.
Deep dive · 4 min
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