Polychords
Two triads played at the same time, one stacked on the other. Each half is something you already know. Together they make a sound neither one can produce alone.
- 6 notes
- two triads
- written as a fraction
which styles use it
- Film music
- Big band
- Twentieth century classical
- Prog
In short
A polychord is two chords sounding together, usually written with one above a horizontal line and the other below it. It is not the same as a slash chord, which puts a single note in the bass. Most polychords can also be named as one large altered chord, and players choose whichever name is easier to read at speed.
A polychord is two pieces of harmony refusing to merge. Your ear hears both at once and cannot settle on either, which is why the sound reads as huge, unresolved, or slightly unreal.
How to build it
- Pick a lower triad as the foundation
This one carries the root and does the job of the ordinary chord. Keep it low and spaced out.
- Put a second triad on top
A whole step above gives the widest, brightest result. A tritone away gives the most tension. Keep the upper triad tight and above the lower one so the ear separates them.
- Check what it adds up to
D major over C major spells C, E, G, D, F sharp and A, which is a C chord with a ninth, a sharp eleventh and a thirteenth. Writing it as two triads is faster to read and faster to play.
Where you run into this
- In twentieth century classical writing, where the technique was made deliberate.
- In big band brass, where two sections each play a triad and the stack is the arrangement.
- In film and game scoring, wherever something enormous or uncanny has to arrive.
The kinds side by side
- Whole step apart: D over C, bright and wide
- Tritone apart: F sharp over C, maximum tension
- Minor third apart: E flat over C, dark and thick
- Same root, different quality: C minor over C major, the crunch of both thirds at once