Symmetrical Polytonality is a harmonic environment in which chord structures arising from symmetrically rich pitch sets/scales suggest several simultaneous tonalities. Symmetrical harmonic structures are the drive mechanism for tonal harmony.

The symmetrical scales and the chords associated with them are also responsible for common non-diatonicism found in music involving the equally tempered chromatic scale. Harmonic symmetries manifest themselves in all styles throughout musical history, and became a primary force upon adoption of the equal tempered tuning system.