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The problem it solves
Once you can build cadences and move along the functional path, you still lack a way to choose the mood and light of the material without leaving the tonal centre. Modes, characteristic notes and borrowed chords are the tools that paint that colour.
Detailed theory
Key idea
The seven diatonic modes come from starting the major scale on each of its degrees: Ionian (1), Dorian (2), Phrygian (3), Lydian (4), Mixolydian (5), Aeolian (6) and Locrian (7).
All the modes of one major scale use the same notes; what changes is which degree acts as the centre, and that recolours them.
This branch works with colour: modes, characteristic notes, borrowed chords and modal interchange, kept apart from the strictly functional path.
Understand it
A mode is a scale you use by giving one particular note the role of centre or tonic. The seven diatonic modes are generated by taking the major scale and starting it on each of its seven degrees: starting on C you get Ionian (mode 1, the major scale itself), on D you get Dorian (mode 2), on E Phrygian (3), on F Lydian (4), on G Mixolydian (5), on A Aeolian (6, the natural minor) and on B Locrian (7).
The key point is that all these modes share exactly the same notes as the parent major scale. D Dorian, for example, uses only the white keys of C major; the only thing that changes is that D is now the centre and the distances from it are different. That is why each mode has its own colour even though it uses the same material.
An analogy: it is the same room photographed from a different doorway. The furniture (the notes) has not moved, but the light comes in from another side and the room looks different. Changing mode is changing the threshold you look at the same set of notes from.
This branch uses that idea to widen tonality without leaving it. Modes provide colours; characteristic notes make that colour audible; borrowed chords and modal interchange bring material from a neighbouring mode into the centre you already have. All of it is colour work over a tonal centre, distinct from the functional motion of dominants and cadences.
To place yourself: after the authentic cadence, instead of asking "where is this harmony pushing", you ask "what light does this material have". The next nodes in the branch unfold each mode, its characteristic note and how to borrow colours from one mode to another.
Staff & keyboard
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The same white keys, now starting on D: D Dorian. The material does not change; the centre has moved from C to D.
How to recognise it
How it's written
When you see a mode written out, first work out the tonic (the centre) and then which major scale shares the same notes. D Dorian, for example, is written with the notes of C major but with D as the centre.
Always compare the mode with a reference scale on the same tonic: that way the altered degree (the characteristic note) jumps out instead of hiding inside a list of notes.
How it feels
Play the C major scale with C as the centre and then the same white keys but resting the phrase on D: you will notice the colour change even though you played no new key. That shift of light with the same material is the essence of modes.
Hold a pedal bass on the tonic of the mode while you play the scale: the fixed centre helps you hear the colour of the mode instead of hearing the usual major scale again.
Common mistake
Thinking each mode is a scale with "new" notes: all the modes of one major scale share the same notes; what changes is the centre.
Confusing modal colour with functional motion: this branch works with the light of the material over a centre, not with paths of dominant and resolution.
Try it
At the keyboard, play the white keys from C to C (Ionian) and then from D to D (Dorian) without changing keys: hear how the centre has moved and the colour with it.
Pick a section of a song you know and ask yourself what light you want: brighter, darker, more open. That question is the gateway to the modal work of this branch.
On the instrument
Staff & keyboard
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The full C major scale: the parent set of notes the seven modes come from. Every key is white.
Reference table
| Mode | Formula | Feel |
|---|---|---|
| Ionian | 1 2 3 4 5 6 7 | Bright; the plain major sound (home, stable) |
| Dorian | 1 2 b3 4 5 6 b7 | Minor but with a bright major sixth (a hopeful minor) |
| Phrygian | 1 b2 b3 4 5 b6 b7 | Dark and tense; the b2 gives a Spanish or exotic colour |
| Lydian | 1 2 3 #4 5 6 7 | Bright, dreamy and floating (the #4) |
| Mixolydian | 1 2 3 4 5 6 b7 | Major but with a b7: bluesy, dominant, rock |
| Aeolian | 1 2 b3 4 5 b6 b7 | The natural minor; sad or serious |
| Locrian | 1 b2 b3 4 b5 b6 b7 | Unstable and dissonant (diminished tonic); rarely a tonal centre |
The seven diatonic modes: the degree formula of each one and the colour or feel it brings. They are all compared on the same tonic.
Where it's used
- Choosing a section's light
- Picking a mode to give a part more brightness or more darkness without changing the tonal centre.
- Widening tonality
- Bringing in colours from a neighbouring mode with borrowed chords and modal interchange without leaving the key.
- Getting your bearings in the branch
- Understanding that the next nodes unfold each mode and its characteristic note from this idea of rotating the centre.
Examples
Staff & keyboard
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Play the C major scale and feel the centre on C. It is the starting point: from here, rotating the centre opens each mode of the branch.
Mini test
Check that you've got it.
0/6 answeredQuestion 1/6
How are the seven diatonic modes built?