I'm trying to understand an interesting non-diatonic chord in the chord progression at 0:30-0:45 of this video; my rough transcription of the chords is as follows.
- As far as I can tell, the non-diatonic chord is a tritone substitution for C#7 (the dominant of the following chord F#m) or C#m7 (the vi in E). Is this a fair assessment of the chord's function?
- Is my naming of G9add13 correct? I don't think it's a G6/9 because of the presence of the F. More generally, is there a broader name for this particular kind of voicing, like "quartal upper structure"?
Thank you again.