Why Does a Ballad Ending Chord Sound Like a Tritone Substitution That Isn’t One?
That chord right before the final tonic in a lot of jazz ballad endings — built a tritone away from where you'd expect a dominant, resolving down by half steps — isn't technically a tritone substitution at all. It's the tonic 6 chord's own upper structure, moved to a different root. Because it shares the identical upper-structure triad, it behaves exactly like a tritone sub without meeting the textbook definition of one. At VoiceLid Jazz Guitar, online jazz guitar lessons with Junewon Choi treat cases like this as proof that upper structures, not roman numerals, explain what's actually happening on the fretboard.
What Chord Is Actually Happening at That Ballad Ending?
Take a tonic 6 chord — say F6. Its upper structure is a minor triad built on the 2nd, which for F6 is D minor. Now raise that same chord's root a #4 away, to B, keeping the same upper structure sitting on top: the result reads as Bm7b5, a diatonic substitute for the tonic. It's still built entirely from the F6 chord's own material — nothing borrowed, nothing altered.
Why Does It Behave Like a Tritone Substitution?
A genuine tritone substitution works because the substitute dominant shares its guide tones (3rd and 7th) with the V chord it's replacing, so the ear hears the same pull toward resolution. This #ivm7b5 chord isn't a dominant at all, and it isn't replacing a V chord — but because it carries the identical upper-structure triad as the tonic, moving the bass note down by half steps underneath that fixed upper structure creates the same kind of forward chromatic pull. The melody note can sit on top the whole time while the harmony underneath does all the moving, resolving on the last chord with the melody landing on the 7th rather than the root.
How Do You Find Upper-Structure Triads Like This Elsewhere in a Tune?
The same logic works forward, not just backward from an ending. Take a minor ii-V-i — Fm7 to Bb7 to Ebmaj7. Voice a G major triad over that Bb7 (it supplies the 3rd, #5, and b7 of an altered dominant sound), and you have one triad-based solution for that 2-5-1. A tune like Stella by Starlight repeats similar ii-V-i motion at other points with different roots. Instead of solving each one from scratch, look for the same triad relationship — a major triad built off the 3rd of the V chord — anywhere the same 2-5-1 shape shows up, and reuse the exact shape you already trust.
What's the Practice Method?
This turns into a repeatable habit rather than a one-time trick:
Find one minor or major ii-V-i in a tune where you already have a triad-based solo solution that works.
Locate a second ii-V-i elsewhere in the same tune, or in a different tune, built on a different root.
Transpose the same triad relationship to that new root and confirm it produces the identical color.
Connect the two spots with common tones so the switch from one key center to the next sounds intentional, not accidental.
How Does This Connect to Superimposition?
This is superimposition in its most practical form: playing a harmonic idea — in this case, a triad — that belongs to a different chord than the one being played underneath, because the two chords share enough structure that the substitution reads as correct rather than wrong. The Bridge Theory material walks through exactly how an upper-structure triad like this connects back to the chord it's replacing, one shape at a time.
For a related but different case — three separate upper-structure triads stacked over a single ii-V-I — see What Is Superimposition on Jazz Guitar?. And the tritone relationship shows up melodically as well as harmonically — Revealing the Tritone in the Django Line traces the same interval through Django's own phrasing.
If you want to see how this same triad-hunting logic maps across the entire neck as one connected system, Fundamental 1: Wes Diagonal System is where VoiceLid Jazz Guitar builds it out in full, from the first shape to the last.
About the Author
Junewon Choi is a Berklee-trained jazz guitarist and the founder of VoiceLid Jazz Guitar, an online education platform teaching jazz harmony and improvisation through the Functional Diagonal Approach (FDA) — a chord-first method built on voice-leading rather than scale boxes.
Wes' Insight — Wes Montgomery's fretboard logic, in lesson form
Fundamental 1: Wes Diagonal System — the FDA from the ground up