Harmony intervals can be divided into three types: extreme harmony, full harmony and incomplete harmony.

Extremely complete harmony interval: pure degree, pure octave.

Complete harmony interval: pure fourth degree, pure fifth degree.

Incomplete harmony interval: size three, size six

Extremely discordant intervals: size two, size seven, and all increments, subtractions, multiples, multiples.

Those intervals that sound discordant are called discordant intervals. For example, the second scale, the seventh scale, and all intervals that are increased or decreased, doubled or decreased belong to dissonance intervals.

In different historical periods, the sum and discord of intervals are different. Different theoretical systems have different classifications.