2. Notes & octaves

← Learning path

Music picks out certain useful pitches and gives them letter names: A, B, C, D, E, F, G (then it repeats). The little # (“sharp”) nudges a note slightly up; b (“flat”) nudges it slightly down.

The number after the letter is the octave — how high up. A4 is the famous one: it wiggles exactly 440 times per second. Go up one octave (A5) and it wiggles twice as fast (880); it sounds like “the same note, but higher.” That doubling is why A4 and A5 feel like siblings.

lead  A4 C5 E5 A5

Real name: the letters are pitch classes; the number is the octave; #/b are accidentals. A4 = 440 Hz is the standard tuning reference the whole system is built around.

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