See the sound

Each note is a harmonic of itself, one octave up.
You could see that just one note C, played on the piano, is heard as one tapering sound to our ears. It actually is a series of waves repeating itself harmonically, as if we have pressed three keys on the keys on the piano simultaneously. Like 400 Hz, 800 Hz, 1200 hz etc.
What a nice graphic to depict sound in picture.