# What is the clearest way to signify the harmonic function of a polychord?

Chords can be analyzed with roman numerals to indicate function:

`C, Am, Dm, G`

`I, vi, ii, V` (or `I, VI-, II-, V` in jazz theory)

And inversions may be analyzed by adding an arabic numeral indicating the note which takes the lowest voice:

`C/G, Am, Dm, G/B`

`I/5, vi, ii, V/3`

But what about polychords, and their ambiguous cousin, slash chords?

`C, Am, Dm, F/G`

`I, vi, ii, IV/2`

The "/2" seems a bit unclear. You could write "IV/V", but that's also a secondary dominant.

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Usually, polychords are written like this: (with a fraction).

So, let's say you have Am {fraction} G7 and we are in the C major scale. You could symbolize that as VIm {fraction} V.

Notice that for the polychords, there is no slash, but a fraction. Slashes are for the slash chords or hybrid chords (inversions).

For the slash chords inversions, if the score you are written isn't really formal, you could write it as `Cmin (1st inv)` or `II(3rd inv)`.

If the score is formal, the first inversion is symbolized with a `6` (actually ^6 -- power of 6) so, you could symbolize Cmin/Eb as I^6, and the second inversion with a `6 4` and the 3rd inversion with a `2`.

If I'm not mistaken, a F/G slash chord, is written as F^9, or IV^9

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Great answer. So for a formal poly chord, it should be written as a fraction. That is consistent with what I've seen too. But what about the "slash" chords? Like F major triad with G in the bass? You could think of it as a G7sus4(9, omit5), but usually it's written "F/C". – Grey Aug 22 '14 at 8:30
If I'm not mistaken, it is written as F^9, or IV^9 – Shevliaskovic Aug 22 '14 at 8:34
Oh I see, yes, indicating the bass note is a tension does kind of get the point across. Good call. – Grey Aug 22 '14 at 8:35