Polychords made easy? (Maybe not)

If you study advanced harmony, you are likely to stumble across the term “polychord” sooner or later.  A polychord is just the result of playing one chord on top of another.

Here is a simple polychord.
Note that we have a D major chord stacked on top of a CMaj7.  You could call it a polychord, but I would not.  I would call it an extended CMaj7 chord or something like that because that is what it really is.  It is a CMaj7 with a 9th, #11th and 13th.

As you get into more complex harmony, labeling something as a polychord is not really very helpful.  I would rather you see every note in relation to the root.  In other words, you need to get to the place where a quick glance at the chord above tells you that it is CMaj7 with a 9th, #11th and 13th.

That being said, thinking in terms of polychords is a great cheat for helping you build complex chords quickly.  For example, if I told you build a EbMaj7 with 9, #11 and 13, a very easy way to do it is to play an EbMaj7 and then play a triad starting a whole note up from Eb.  If you play F Major on top of EbMaj7, you have your chord.  You might change around the order of the notes of course and may leave a note or two out of course but that will not change what the chord is.

We call this kind of thinking polychord voicing.  Here are a few of the more common polychord voicings and what they end up being in terms of an extended chord.

Start with Add Result
Dominant Major triad up a whole step Dominant with 9, #11, and 13
Dominant Major triad up a tritone Dominant with b9 and #11.
Dominant Major triad up a minor 6th Altered dominant (#9 and b13)
Dominant Diminished 7th up a half step Dominant with b9
Minor 7th Minor triad up a whole step Minor 7th with 9, 11, and 13
Major 7th Major triad up a whole step Major 7th with 9, #11, and 13

When you add these chords, remember that you don’t have to play them as a block chord.  Let’s say that you want to play C7(b9).  You could play C7 in the left hand and a Dbdim7 as an arpeggio in the right hand like this:

So this is the moral of the story.  Polychords are a great cheat to easily play extended chords but they are a bad way of labeling chords.  If you use them, always know what you are playing in relation to the root so you can understand the function of the chord.