You already know two modes without realising it. The major scale is Ionian mode. The natural minor scale is Aeolian mode. Modes are what happen when you play the same seven notes but treat a different note as home. Same ingredients, different starting point, completely different flavour.
Modes: same notes, different centre
Take the C major scale (C D E F G A B). Now play those exact same notes, but start and resolve on D instead. The pattern of tones and semitones changes relative to your new root, giving a different mood. That's D Dorian.
The seven modes of C major
Mode I: Ionian (the major scale)
You already know this one. Bright, happy, resolved. The "default" mode. Pattern: T-T-S-T-T-T-S.
C Ionian (C major) - the familiar starting point
Mode II: Dorian
Minor but brighter than natural minor. The difference: the 6th degree is raised (major 6th instead of minor 6th). Pattern: T-S-T-T-T-S-T. Semitones: 0, 2, 3, 5, 7, 9, 10.
D Dorian - same white keys as C major, centred on D
Mode III: Phrygian
The darkest common mode. The b2 (one semitone above the root) gives it an exotic, tense quality. Pattern: S-T-T-T-S-T-T. Semitones: 0, 1, 3, 5, 7, 8, 10.
E Phrygian - that b2 (F, one semitone up) is the signature sound
Mode IV: Lydian
The brightest mode. Major with a raised 4th (#4), which creates a dreamy, floating quality. Nothing in this scale wants to pull downward - everything lifts. Pattern: T-T-T-S-T-T-S. Semitones: 0, 2, 4, 6, 7, 9, 11.
F Lydian - the raised 4th (B natural) gives it that floating feel
Mode V: Mixolydian
Major with a flat 7th. It's the sound of dominant 7th chords and has a bluesy, laid-back feel. Pattern: T-T-S-T-T-S-T. Semitones: 0, 2, 4, 5, 7, 9, 10.
G Mixolydian - same as G major but with F natural instead of F#
Mode VI: Aeolian (natural minor)
Another one you already know. The natural minor scale is Aeolian mode. Pattern: T-S-T-T-S-T-T. Semitones: 0, 2, 3, 5, 7, 8, 10.
A Aeolian (A natural minor) - the standard minor sound
Mode VII: Locrian
The most unstable mode. It has both a b2 and a b5 (diminished fifth from root), making it difficult to feel settled. Rarely used as a key centre, but important in theory. Pattern: S-T-T-S-T-T-T. Semitones: 0, 1, 3, 5, 6, 8, 10.
B Locrian - the diminished 5th makes it inherently unstable
The brightness spectrum
Modes can be arranged from brightest to darkest. This is determined by how many notes are raised or lowered compared to major.
Key takeaway
Seven modes from one major scale, each starting on a different degree. Three are major-type (Ionian, Lydian, Mixolydian), three are minor-type (Dorian, Phrygian, Aeolian), and one is diminished (Locrian). You already knew two of them as the major and natural minor scales.
Next: how modes are actually used in different genres of music.
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