What a note is

Music is made of sounds, and sounds differ in several ways at once: how loud, how long, and how high. That last one is pitch, and almost everything else here depends on it. Pitch comes from how fast the air is vibrating — faster vibration, higher sound — though you never have to think of it that way to hear it.

Nothing in this lesson belongs to one instrument. A guitarist and a pianist learn exactly the same seven names, in the same order, and meet them in the same place.