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II.9Part II, Scales and Intervals
Consonant and Dissonant Intervals
This lesson teaches you to classify every harmonic interval as a perfect, imperfect or mixed consonance, or as a dissonance.
6 min9 questionsDanhauser § 102 and 103
When two notes are heard at the same time, they form a harmonic interval. When you hear them one after the other, they form a melodic interval.
Consonance and dissonance
Harmonic intervals fall into two groups: consonances and dissonances.
A consonance is made of two notes that the ear feels no need to pull apart. It gives an impression of unity, cohesion and stability. These, says Danhauser, are the sounds produced by the resonance of a single generating tone, that is, its first harmonics, which you'll study in the next part.
A dissonance is made of two notes that the ear wants to change, to replace with other notes. It gives an impression of instability: the notes tend to move apart and arrive at a consonance.
Table of consonant intervals
Type
Intervals
Perfect consonances
perfect octave, perfect fifth
Imperfect consonances
major third, minor third, major sixth, minor sixth
Mixed consonance
perfect fourth
Only consonant intervals are divided into types. All the others are dissonant.
Dissonances
All seconds, all sevenths, and all diminished or augmented intervals are dissonant. That includes the major second, the minor seventh, the diminished fifth, the augmented fourth, and many others.
Listen to harmonic intervals: first ask yourself “stable or unstable?”, then name them.
Intervals in play
Tip: link each interval to the opening of a tune you know well, then check it in the interval lab.
Exercisein the method's spirit
For each of these harmonic intervals, say whether it is consonant or dissonant, and give the type of each consonance: C-G, D-F, E-D, F-B, G-E, A-A (an octave), B-D, C-F, D-E, E-C.
Solution
C-G is a perfect fifth, a perfect consonance. D-F is a minor third, an imperfect consonance. E-D is a minor seventh, a dissonance. F-B is an augmented fourth, a dissonance. G-E is a major sixth, an imperfect consonance. A-A is a perfect octave, a perfect consonance. B-D is a minor third, an imperfect consonance. C-F is a perfect fourth, a mixed consonance. D-E is a major second, a dissonance. E-C is a minor sixth, an imperfect consonance.
That completes our study of intervals. In the next part, we'll put them to work to build the major scale.
Check your understanding
9 questions
1.
Which intervals are the perfect consonances?
2.
Danhauser classifies the perfect fourth as:
3.
The minor sixth is:
4.
The major second is:
5.
The diminished fifth is:
6.
Two notes heard at the same time form:
7.
According to Danhauser, what impression does a dissonance give?
8.
What is the frequency ratio of the pure perfect fifth?
9.
Classify this harmonic interval.
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