Tonality in the form of consonance and dissonance are the building blocks of harmony in music. They are created when two or more tones are played simultaneously. Unison, third, fifth, sixth, octave, and the intervals made up of these and the octave are consonances. Some of these are perfect consonances, the others imperfect. The unison, third, and fifth are perfect. The sixth, and third are imperfect. The remaining intervals, like the second, fourth, diminished fifth, tritone, seventh, and the intervals made up of these and the octave, are dissonances.

A progression through a variety of these intervals creates an emotional response in the listener that we call music. The progression of intervals is created by the motion of the tones (voices) within the intervals in three possible movements: Direct, Contrary, or Oblique.