Intervals can be classified as consonant or dissonant according to the complexity of the mathematical relation between the notes pitches.
Although this concept has changed during musical history and even today not all theoreticians agree, we can offer the following classification:
Consonant | Dissonance |
---|---|
Unison | Second |
Major and minor third | Perfect fourth (considered a dissonance in harmony and counterpoint) |
Perfect fifth | Seventh |
Major and minor sixth | Augmented fourth |
Perfect octave | Diminished fifth |
See Reading Music in the Tutorials section.