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"The type of triad on each degree of a minor scale is the same for every harmonic and melodic minor scale" in TCL grade 6 theory. What is meant by this?
I guess the types of chords are major, minor, augmented and diminished. How come the above statement is true? For example, we do not have augmented triads in natural minor scale.
The statement
The type of triad on each degree of a minor scale is the same for every harmonic and melodic minor scale
can be restated:
The reason for this is that each type of minor scale is defined by a unique series of intervals. The illustration below shows the interval sequence for each minor scale type and a table of the triads that can be formed within each scale type.
M2 m2 M2 M2 m2 M2 M2
| Scale degrees | Thirds | Chord quality |
|---|---|---|
| 1 3 5 | m3 M3 | minor |
| 2 4 6 | m3 m3 | diminished |
| 3 5 7 | M3 m3 | major |
| 4 6 1 | m3 M3 | minor |
| 5 7 2 | m3 M3 | minor |
| 6 1 3 | M3 m3 | major |
| 7 2 4 | M3 m3 | major |
M2 m2 M2 M2 m2 A2 m2
| Scale degrees | Thirds | Chord quality |
|---|---|---|
| 1 3 5 | m3 M3 | minor |
| 2 4 6 | m3 m3 | diminished |
| 3 5 7 | M3 M3 | augmented |
| 4 6 1 | m3 M3 | minor |
| 5 7 2 | M3 m3 | major |
| 6 1 3 | M3 m3 | major |
| 7 2 4 | m3 m3 | diminished |
M2 m2 M2 M2 M2 M2 m2
| Scale degrees | Thirds | Chord quality |
|---|---|---|
| 1 3 5 | m3 M3 | minor |
| 2 4 6 | m3 M3 | minor |
| 3 5 7 | M3 M3 | augmented |
| 4 6 1 | M3 m3 | major |
| 5 7 2 | M3 m3 | major |
| 6 1 3 | m3 m3 | diminished |
| 7 2 4 | m3 m3 | diminished |
As it stands, that statement is ambiguous. True, each triad made from the harmonic minor notes will be the same (for each key), and each triad made up from the melodic minor notes will be the same. (I mean - maj., min., dim., or aug.)It doesn't clearly state that, though. And then I guess we must involve the notes of the descending melodic (same as natural minor) as they will produce some different triads from the ascending melodic minor notes.
The statement needs a tidy up!
The type of triad formed on a given degree of a harmonic minor or melodic minor scale is the same, irrespective of the key of the scale.
For example, the triad formed on the second degree of the D minor harmonic scale will be the same type of triad one would get by forming a triad on the second degree of, say, the E minor scale; i.e., both are diminished.
The natural minor scale, or aeolian mode, is identical to the descending version of the melodic minor scale. Therefore all of the triads found using notes from the natural minor scale can be formed using notes from the melodic minor scale.
