Twelve TheoryMath + Music Playground
Explore interactive music theory and music by numbers through Free Play, Math Mode, Chord Game, Harmonic Cone, Waveforms, Harmonic Polygons, Sheet Music, Musical Circles, and Ear Training.
Free play
Keyboard view
Number-pad pianoHold multiple keypad numbers to play them together.
Computer keyboard1–90 or * = 10− = 11= = 12O = octave downP = octave upEnter = next
Press and hold a number to hear it.
Play scale from
Just tuning uses pure major-scale ratios around one selected key. Equal temperament unlocks every key.
Hold a pad to sustain it and release to stop. Hold multiple pads to hear the tones together.
Odd tonic: 3 consecutive odds → 4 consecutive evens → tonic
Even tonic: 3 consecutive evens → 4 consecutive odds → tonic
From 1: 1–3–5–6–8–10–12–1From 2: 2–4–6–7–9–11–1–2
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