§ 00 · Visual overview

Hear the shape.
Don't just read the notes.

Music is organized vibration. Every note is a frequency, every interval a ratio, every chord a stack of waves, every groove a grid in time. Everything below makes sound — press, drag, and listen. Turn your volume on.

a living waveform its harmonics Every sound you'll ever hear is some version of this picture. Click it to hear the wave it's drawing.
§ 01 · Pitch is frequency

A note is just a number

Drag the slider: faster vibration = higher pitch. Double the frequency and you land on the same note, one octave up — that ×2 trick is the foundation of all music.

A4 = 440 Hz  ·  octave up = × 2  ·  semitone = × 2^(1/12)
Frequency
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Nearest note
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Off by
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Wave period
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Land the "off by" readout on 0 cents and you've tuned by hand — the same game a guitar tuner plays. A cent is a hundredth of a semitone.

§ 02 · The keyboard map

Twelve keys, then it repeats

Play it — click, tap, or use your computer keys (A S D F … are white keys, W E T Y U … are black). Every neighboring key is exactly one semitone apart; after 12 of them the pattern starts over, one octave higher.

Last note
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Frequency
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Semitones from C4
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Octave
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The black keys have two names each — C♯ is the same key as D♭. Which name you use depends on context, but the sound is identical: that's called being enharmonic.

§ 03 · Intervals — distance you can hear

Harmony is a ratio

Pick an interval and listen. When the two frequencies form a simple ratio like 3:2, the waves lock together and it sounds smooth. Messy ratios wobble and clash — you can see the difference in the combined wave below.

P5 ≈ 3:2  ·  P4 ≈ 4:3  ·  M3 ≈ 5:4  ·  tritone ≈ 45:32 (ouch)
root note interval note the two added together — smooth pattern = consonant
Interval
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Semitones
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Frequency ratio
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Character
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Try the tritone (6 semitones), then the perfect fifth (7). One extra semitone turns medieval "devil's interval" tension into the most stable sound in music. Your ear is doing ratio math without being asked.

§ 04 · Scales — a recipe of steps

Seven notes from one pattern

A scale is just a step recipe applied to any starting note. Major = W W H W W W H (whole and half steps). Pick a root and a flavor — the highlighted keys and the sound follow automatically. Click any lit key to hear it.

Scale
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Step pattern
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Notes
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Now playing
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Play C major, then C minor. Only three notes change, but the mood flips completely. Then try the pentatonic — five notes chosen so that almost any order sounds good. It's the training wheels of improvisation.

§ 05 · Chords — notes in a stack

Three notes, one feeling

Stack a note, the note 3 or 4 semitones up, and one more on top — that's a triad, the atom of harmony. The spacing of the stack is the whole difference between happy, sad, tense, and dreamy.

major = 0 · 4 · 7  ·  minor = 0 · 3 · 7  ·  dim = 0 · 3 · 6  ·  aug = 0 · 4 · 8
Chord
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Notes
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Semitone stack
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Mood
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Now playing
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Flip between C major and C minor a few times — one key moves by one semitone. That single semitone is doing all the emotional work. Then hold the 7th chords: one extra note adds the color you hear all over jazz and R&B.

§ 06 · Rhythm — the grid in time

A beat is a pattern of yes and no

Sixteen boxes = one bar of sixteenth notes. Click boxes on, press play, drag the tempo. You are now a drum machine. Start with kick on 1, 5, 9, 13 and snare on 5 and 13 — then break the rules.

Step
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Bar position
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Sixteenth length
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Push the swing slider up while it plays: every off-beat sixteenth gets delayed, and the same boxes suddenly groove instead of march. Swing isn't a different pattern — it's the same pattern with bent time.

§ 07 · Ear trainer

Now close your eyes and listen

Everything above was for your eyes. These two games are for your ears — the only music skill that compounds forever. No streaks, no penalties. Guess, listen again, guess again.

Game 1 · Name that interval
Press “Play” — two notes will play, low then high. Press it again anytime to hear them once more.
Correct
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Attempts
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Accuracy
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Game 2 · Major, minor, or something weirder
Press “Play” — a triad will play as a block. Press it again anytime to hear it once more.
Correct
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Attempts
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Accuracy
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Stuck on intervals? Anchor them to songs you know: a perfect 4th is the first two notes of "Here Comes the Bride," a major 6th opens the NBC chime, an octave opens "Somewhere Over the Rainbow." Your memory already contains the answers.