Modal interchange, sometimes called modal mixture, is a guitar technique through which you combine chords from parallel scales. A parallel scale is any scale that starts on the same pitch. For example, the A major scale and the A minor scale are parallel. Because the tonic pitch remains the same with modal interchange, it isn’t considered a key change.
However, you do play, or borrow, chords from other keys (which is where the term borrowed chord comes from).
Here are seven different scales and sets of chords that start on A. The first six are modes from the major scales Ionian through Aeolian. The last scale is the A harmonic minor. Because harmonic minor occurs only on the V chord, the chords have been written for A harmonic minor by using A natural minor (Aeolian) for everything except V7, the most defining characteristic of harmonic minor.
| Scale/Mode | Numbers/Chords |
|---|---|
| A Ionian (major scale) | A-Bsm-Csm-D-E-Fsm-Gsmf5 I-ii-iii-IV-V-vi-viif5 |
| A Dorian | Am-Bm-C-D-Em-Fsmf5-G i-ii-fIII-IV-v-vif5-fVII |
| A Phrygian | Am-Bf-C-Dm-Emf5-F-Gm i-fII-fIII-iv-vf5-fVI-fvii |
| A Lydian | A-B-Csm-Dsmf5-E-Fsm-Gsm I-II-iii-sivf5-V-vi-vii |
| A Mixolydian | A-Bm-Csmf5-D-Em-Fsm-G I-ii-iiif5-IV-v-vi-fVII |
| A Aeolian (natural minor) | Am-Bmf5-C-Dm-Em-F-G i-iif5-fIII-iv-v-fVI-fVII |
| A harmonic minor | Am-Bmf5-C-Dm-E7-F-G i-iif5-fIII-iv-V7-fVI-fVII |
With all these chords to choose from, you have the potential to compose a great variety of chord progressions. Pretty cool, right?