Twelve TheoryMath + Music Playground

Explore interactive music theory and music by numbers through Free Play, Math Mode, Chord Game, the Note Stage, Circle Counting, the Triad Chart, Harmonic Cone, Waveforms, Harmonic Polygons, Tuning String, Sheet Music, Musical Circles, and Ear Training.

The Note Stage

Pick the star. Hear the key come alive.

Every character owns one note. Tap any combination to build a singing scale, chord, or cluster.

Odd · purpleEven · pink
Key family
Now onstageC major1 C is the tonic

Choose the star, then tap any character to hear their voice.

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