What are the official modes from Ionian to Locrian?

Question

I am having some confusion is respects to the formal definition of what the various modes are. I know that their defined in relation to their scale, however, I've come to realise this may not be best way to define it. For instance, the Phrygian mode of the minor scale is the major mode, as follows: T ST T T ST T T T T ST T T T ST The Aeolian mode of the Major scale is also the natural minor scale. However, because these two scales are one of the same, they have the same modes. However, the 'Dorian' mode of each scale is different, so is the Phrygian mode, and so on. Thus we *could* say we have 14 modes, but only 7 are unique. So what is the official status quo on this? Also, I know that there are other modes which have a *completely* different arrangement, but the major and minor modes or scales, at least is respects to Western culture, dominant at least 95% of music, likely more (that's also accounting for the 7 modes, not just the natural minor/major scales). And as the two are the same, this is way I was wondering if there is a formal definition of the unique modes. To those scales which are unique, would the modes that are then formed be given the same titles as the modes of the major/minor scale? If I may ask another but related question - I hear there are many, many modes out there, but how many are actually unique? As an ambiguous example, say there were 1000 out there, only say, maybe 50 of them could be unique. By the way, by unique, I mean in the sense that they have a different sequential arrangement of semitones, but if two modes share the same sequence, regardless of order, then their combined total of modes is equal to the sum of just one of the original modes.

Answer 1

If you play the white keys on a piano from A to A, that is the Aeolian mode, identical to the pure minor scale. B to B on the white keys is Locrian, C to C is Ionian, same as the major scale. D to D is Dorian, E to E is Phrygian, F to F is Lydian and G to G is Mixolydian. Of course one can start on any note and build one of these Ecclesiastical modes as long as the whole and half steps are in the correct place. The Plagal Modes are the same but start a fourth lower than the white key versions. These are the only modes that exist and I believe you may be making this more complicated than it really is.

Answer 2

The diatonic modes, or the "church" modes as they are sometimes called, basically come about by shifting the interval structure of whole and half steps, just as you have noticed, of the major scale. Also, as you mention, there are far more modes than just these, but let's start with the ordering of the diatonic "church" modes.

Ionian, Dorian, Phrygian, Lydian, Mixolydian, Aeolian, Locrian and back to Ionian.

Now, Ionian is the naturally occurring major scale. Think of it appearing as C to C on the piano playing only the white keys. Now, if we do the same thing, but starting on D, again playing only the white keys of the piano, we would hear the Dorian mode; E to E on only white keys is the Phrygian mode, F to F is Lydian, G to G is Mixolydian, A to A is Aeolian which is otherwise known as the natural minor scale, finally B to B on only white keys is the Locrian mode.

We tend to think of each of these modes as being either major or minor based on the quality of their third. Ionian, Lydian, and Mixolydian are considered major modes, while Dorian, Phrygian and Aeolian are minor. Locrian can be considered minor too, but to be honest it's more of an afterthought. The tonic triad in Locrian is diminished and makes it incredibly difficult to function harmonically.

Since they are grouped in major and minor we can think of them as being major or minor scales with single alterations. Dorian is a minor scale with a raised 6th degree, Phrygian is a minor scale with a lowered 2nd degree, Lydian is major with a raised 4th degree, Mixolydian is major with a lowered 7th degree, and Locrian, again, being an oddity, is like a minor scale with a lowered 2nd and 5th scale degree.

It is true, there are many, many modes out there. I can not be sure how many are unique, but know that scales do not necessarily have to have only 7 pitches: they can contain more, like the octatonic scale, or less like the pentatonic and hexatonic scales. Olivier Messiaen was fascinated by "modes of limited transposition" and would write music using them. There are also modes of the melodic minor scale, and modes of the harmonic minor scale, as well as many others.