What it is
Chord-scale theory associates with each chord one or more compatible scales, based on its quality, its function and the context of the key. It was systematized mainly at Berklee (Barrie Nettles and Richard Graf, The Chord Scale Theory & Jazz Harmony, 1997) and relies on ideas from George Russell (Lydian Chromatic Concept). It is the standard tool for improvising, writing melodies over chords, choosing the tensions of voicings and arranging.
Key concepts
- Chord tones: 1, 3, 5, 7.
- Available tensions: 9, 11, 13 (and the altered ones on dominants) that can be added to the voicing or held in the melody.
- Avoid notes (notes to avoid as long notes): usually a note a semitone above a chord tone, which creates a minor 9th. Examples: the 4th (F) over Cmaj7; the b2 and b6 over Em7 (iii); the b6 over Am7 (vi); the 4th over G7. On dominants the b9 and b13 are not “avoid” but altered tensions.
- Avoid notes are not forbidden: they are used as passing notes, on weak beats.
The procedure in 4 questions
- What quality does the chord have? (maj7, m7, 7, ø7, °7, m(maj7), sus…).
- What function does it have in the key? (I, ii, iii, IV, V, vi, secondary dominant, borrowed chord, substitution).
- Which notes are imposed by the melody and the key? (the diatonic notes of the key take precedence).
- What color do I want? (more consonant and “inside”, or more tense and “outside”).
Reference table
| Chord / function | Main scale | Alternatives | Typical tensions | Avoid |
|---|---|---|---|---|
| Imaj7 | Ionian | Lydian, major pentatonic | 9, 13 | 4 (F) |
| IVmaj7 | Lydian | Ionian | 9, #11, 13 | — |
| bVImaj7 (borrowed) | Lydian | Lydian #2 (in harmonic minor) | 9, #11 | — |
| iim7 | Dorian | — | 9, 11, 13 | (13 if it creates a tritone with the 3rd in a tonal context) |
| iiim7 | Phrygian | Aeolian | 11 | b9, b13 |
| vim7 | Aeolian | Dorian (in a modal context) | 9, 11 | b13 |
| V7 (toward major) | Mixolydian | dominant bebop, Lydian dominant | 9, 13 | 4 |
| V7 (toward minor) | Phrygian dominant | altered, half-whole diminished | b9, b13, #9 | 4 |
| V7alt | altered (Super Locrian) | — | b9, #9, b5, b13 | — |
| V7b9 with 13 | half-whole diminished | — | b9, #9, #11, 13 | — |
| V7#11, bVII7, IV7 of the blues, SubV7 | Lydian dominant | Mixolydian, blues | 9, #11, 13 | — |
| V7#5 / 9#5 | whole-tone | altered | 9, #11, #5 | — |
| V7sus4 | Mixolydian (the 4 is a chord tone) | suspended pentatonic | 9, 13 | 3 |
| 7sus4(b9) | Dorian b2 | Phrygian | b9, 13 | — |
| iiø7 (in minor) | Locrian | Locrian #2, Locrian #6 | 11, b13 (9 with the #2) | b9 (in Locrian) |
| vii°7 | whole-half diminished | Super Locrian bb7 (harmonic minor) | 9, 11, b13, 7 | — |
| i m(maj7) / im6 | melodic minor | harmonic minor, Dorian (m6) | 9, 11, 13 | — |
| maj7#5 | Lydian augmented | Ionian #5 | 9, #11 | — |
| Secondary dominant V7/x | Mixolydian with the accidentals of the target key | Phrygian dominant if it arrives on a minor chord | 9, 13 or b9, b13 | — |
How to “read” a ii–V–I
C major: Dm7 (D Dorian) – G7 (G Mixolydian, or altered for more tension) – Cmaj7 (C Ionian or Lydian). In practice the first two scales have the same notes as C major: chord-scale theory makes the arrival notes of each chord explicit.
C minor: Dø7 (D Locrian or Locrian #2) – G7b9b13 (G Phrygian dominant) or G7alt (altered) – Cm(maj7) (C melodic minor) or Cm7 (C Dorian/Aeolian).
Criticisms and limits
- Mark Levine (The Jazz Theory Book) and many educators remind us that scales should not be played up and down: they are reservoirs of notes. Melody comes from chord tones, guide tones, chromatic approaches and motifs.
- The “one scale per chord” (vertical) approach can make lines fragmented: the horizontal approach (one parent scale for several chords, as in the Lydian Chromatic Concept) or bebop thinking (chord tones on the downbeats) give more continuity.
- In pop music and in production loops the scale of the key is often enough, with attention to the long notes over the chords: chord-scale theory is mainly useful when chromatic chords come in.
Practical use for a producer
- When you write a topline over a loop, check the long notes: they must be chord tones or available tensions.
- For pads and voicings: add the tensions from the table (9 and 13 on maj7, 9 and 11 on m7, b9 and b13 on dominants toward minor).
- For color changes: the same progression sounds different by choosing different scales (G7 Mixolydian = “pop”, G7 altered = “jazz”).
- In the FL Studio Piano roll you can change “Scale highlighting” at every section to see the notes of the chord’s scale.
Exercise
- Take “Autumn Leaves” (in G minor) and write a scale for each chord; then improvise using only chord tones on the downbeats.
- Over a loop Cmaj7 – A7 – Dm7 – G7, choose three different scales for A7 (Mixolydian with the notes of D minor, Phrygian dominant, altered) and compare.
- Write a topline over one of your loops and check every long note against the table: replace the avoid notes on strong beats.
Related
All the modes of the major scale, of melodic minor and of harmonic minor; Extensions and tensions; The jazz ii–V–I; Lydian Chromatic Concept; Bebop scales; Guide tone lines.