Two different concepts
- Hybrid chord (hybrid chord, Berklee): a triad (or seventh chord) over a bass note that is neither its root nor one of its notes. It is written with a slash: Bb/C, D/C, F/G. The upper triad and the bass together form an extended chord without a third or with ambiguous functions.
- Polychord: two complete chords stacked, each one recognizable. It is written with a horizontal line (upper chord above, lower chord below); here we indicate it as “E over C.”
Main hybrids (bass C)
| Symbol | Notes | Equivalent | Use |
|---|---|---|---|
| Bb/C | C Bb D F | C9sus4 | suspended dominant, gospel, pop |
| Gm7/C | C G Bb D F | C9sus4 (with 5) | same as above, fuller |
| D/C | C D F# A | D7/C, or C Lydian (9, #11, 13) | Lydian color over a C pedal |
| E/C | C E G# B | Cmaj7#5 | melodic minor, dreamy |
| Ab/C | C Ab C Eb | Ab/C (first inversion of Ab) | not a hybrid: it is an inversion |
| Gb/C | C Gb Bb Db | C7(b9 #11) without the third | tense dominant |
| Db/C | C Db F Ab | C Phrygian (b9, 11, b13) | suspended Phrygian |
| Eb/C | C Eb G Bb | Cm7 | not a hybrid: it is Cm7 |
Rule: if the triad contains the bass note or forms a standard chord with it, it is not a hybrid but an inversion or an ordinary chord.
The most widely used hybrid dominant
F/G (G F A C) = G9sus4 (G, 7, 9, 11). In place of G7 before C: it has no tritone, so the tension is soft; it resolves well to C or to C/E. It is the “gospel” and “modern pop” dominant par excellence.
Famous polychords
- Petrushka chord (Stravinsky, Petrushka, 1911): C major over F# major (C E G + F# A# C#), two triads a tritone apart, played by two clarinets. It symbolizes the puppet’s dual nature.
- Augurs chord (The Rite of Spring, 1913): an Fb major (enharmonically E major) in the low registers and an Eb7 above it, repeated with irregular accents.
- Upper structure in jazz: a major triad over a dominant chord (D over C7 = C13#11) is a “tamed” polychord.
How to build polychords that work
- Register separation: lower chord below C4, upper chord above C4; at least an octave between the centers.
- Different timbres: strings below, winds above; or piano left hand and synth pad.
- Relationship between the roots: tritone (maximum contrast), major second (Lydian, bright), major third (augmented), semitone (extreme dissonance).
- Dosage: a polychord held for a long time becomes a color; used briefly it is a “punch.”
Listening examples
- Petrushka (second tableau) for the tritone polychord.
- Maiden Voyage by Herbie Hancock: chords such as Am7/D and Cm7/F are hybrids (= D11 and F11 without the third), the basis of the 1960s modal sound.
- Pop and gospel ballads: F/G, Bb/C, Eb/F before the tonic.
Producer exercise
- Write C – F/G – C on a pad: compare with C – G7 – C.
- Create a loop of two hybrids: D/C – C (4 bars each) for a Lydian intro.
- Try a “Petrushka” polychord: C major in the high strings, F# major in the low brass, for 2 bars; then resolve to C. Use EQ to separate the registers (HPF at 300 Hz on the high strings, LPF at 2 kHz on the low brass).
Related topics
Sus, add, slash, and hybrid chords (basic lesson), upper structure triads, polytonality, sus chords and polymodality, slash chords in pop.