Minor Scales Revisited
In the natural minor scale lesson, we briefly touched on the fact that there were a number of different scales. The reasons for this are fascinating, and we now have enough theory to understand a bit more about why this might be. In adition, we have also spoken about various modes of the major scale being minor in nature. Lets pull all of this together and look a little more into minor scales.
A minor scale is defined as:
"a diatonic scale where the third note ("scale degree") is a minor third" (rather than a major third).
(Diatonic means that the scale is constructed using some variation of all 7 whole notes available - A B C D E F G).
To begin with, of the major modes, four are minor by this definition:
Dorian, Phrygian, Aeolian and (to some) Locrian.
Locrian is such a special mode (because it's the only mode of major that doesn't have a perfect fifth), so we rarely count it as minor (or major for that matter). There's more about that in my "Modes an alternative view", here.
Mostly, however, when we speak of minor, we mean Aeolian mode, and two (or three) variations on it.
We'll take a tour of these now, looking specifically at variations of the C minor scale.
The Natural minor and its problem
C natural minor: C D Eb F G Ab Bb C
Formula : 2 1 2 2 1 2 2
Intervals : 1, 2, b3, 4, 5, b6, b7
After early musicians started to work on variations of the aeolian mode, we started to speak of aeolian mode as natural minor, since it was "naturally" derived from the major scale (in other words, it was a mode of major).
The "problem" with the natural minor scale is its 7th scale degree (note) (the red in the first formula above shows this "problem"). Western composers were used to the fact that the 7th note in the scale was one semitone below the root note, as it is in the major scale:
C major: C D E F G A B C
Formula : 2 2 1 2 2 2 1
As you can see, there is only 1 semitone from B to C.
This 1 semitone interval has an important harmonic function in a major scale - B really wants to resolve to C. If we play the C major scale from C up to B and stop there, the B really "wants" to lead us on to C, to give a sense of closure. Which is why we call the 7th note in major scales "the leading tone". This has all kinds of implications for harmony, choice of chords etc. It's rather important in (especially classical period) western music.
But we don't have one semitone at the end of the our natural minor scale:
C D Eb F G Ab Bb C
Rather we have two semitones - from Bb to C in our C natural minor example. This doesn't have the same effect. And since that one semitone was so important in western harmony, they decided to "fix" it, by raising the 7th scale degree. In C minor, that means changeing the Bb to B, which gives us the harmonic minor scale.
Harmonic minor - and its problem
C Harmonic minor : C D Eb F G Ab B C
Formual : 2 1 2 2 1 3 1
Intervals : 1, 2, b3, 4, 5, b6, 7
Now we have Aeolian mode, but with a major 7th. We call that harmonic minor, because of the leading tone's important harmonic function.
But in return, we also got a 3 semitone step - unusual in the scales and modes we have dealt with so far, apart from the pentatonics. From the 6th scale degree to the 7th scale degree - Ab to B. Many composers (but not all) felt an interval of 3 semitones was unmelodic. It was hard to sing, and it sounded "oriental". What to do about that, then? Simple, they also raised the 6th scale degree, to get the Melodic Minor scale.
(Ascending) melodic minor - and its problem
C Melodic Minor : C D Eb F G A B C
Formula : 2 1 2 2 2 2 1
Intervals : 1, 2, b3, 4, 5, 6, 7
Initially, this was called melodic minor, as compared to the "unmelodic" harmonic minor. But now we're almost playing major, except for the flat (minor) 3rd scale degree. So minor doesn't really sound so different from major anymore. What to do?
Full melodic minor
This problem was solved by using two scales in combination. When a melody is going upwards, we use the melodic minor, because we need that leading tone - going from B to C. When going downwards, however, we have no use for the leading tone - it's not as important harmonically whether we go from C to B or from C to Bb. So, going downwards, we use natural minor (aeolian mode):
Up -> Down ->
C D Eb F G A B C Bb Ab G F Eb D C
That's the full melodic minor scale. Upwards, we use what was eventually called the ascending melodic minor, downwards we use the descending melodic minor - which is exactly the same as aeolian mode. That way, we keep the feeling of the aeolian scale, but get our beloved leading tone, and avoid sounding oriental.
(This is not entirely consistent, when you actually look at works of various composers - they may use ascending melodic minor when going downwards, and descending when going upwards... It all depends on how well they could accept the various pros and cons of the different minor scales). The end result is that often you can freely use natural, harmonic or melodic minor in a piece in a minor key.
So, to summarize, when we talk about a minor scale, we're mostly talking about natural (aeolian), harmonic or melodic minor, although we may also include the dorian and phrygian modes. When we say the minor scale, all bets are off. Most people would probably mean natural minor, while a music professor would refuse to even use such a term, and others might tell you melodic minor is the minor scale.
This lesson virtually in its entirety was taken with permission from a post by Kaneda, minor edits by me. Thanks Kaneda!