# How do I write the roman numeral symbol for 6 chords and tritone substitution chords?

1. Am6 in the key of A minor. (or just 6 chords in general) Is there a correct way to write this or do I just write "i"? I can't use i6 cause that obviously means an inversion. What about 6 chord inversions? (Ex. G6/B still in the key of A minor)

2. Tritone substitutions? So let's say I substitute E7 (still key of A minor) with Bb7. What's the roman numeral symbol for that?

• Am6 wouldn't be written in isolation - so the reader wouldn't consider it to be an inversion.
– Tim
Aug 18, 2022 at 7:59

The figured bass way of specifiying a chord with an added 6th would be 56, which is also the first inversion of a seventh chord.

If you invert such a chord you arrive at 34 chord (also the second inversion of a seventh chord). So the first inversion of i56 would be iii34 (if you use the roman numerals for the bass note) or vi56 and vi34 (if you use them for the "root" note).

And if you substitute a Bb7 into Am you can simply use bII. There is also use of symbols like bV7/V or V7/bV and subV7, the first two meaning the low alterated secondary dominant of the dominant and the secondary dominant of the low altered dominant, and the third one just meaning V7 with tritone substitution.

• I've generally found that bII is a lot more common than bII7, so any use of bII7 should be specifically pointed out. Unusually, one of the few times I have heard bII7, it resolved outward (to i6/4 - V), so it sounded more like a weird augmented 6th chord than a genuine (minor-major/"dominant") 7th chord. Aug 18, 2022 at 16:37