Upper Structures

An upper structure is a triad played in the upper register over a different chord (or just a bass note) below it. The two layers fuse into one big, extended chord, yet each hand only plays something simple.

Hear it with the plainest example. Play a C in the bass. Now float an E major triad (E G# B) above it. Against C, those three notes are the 3, the #5 and the 7, so the whole thing is Cmaj7#5: a bright, slightly unstable major chord that no beginner would know how to spell. Yet you just played a C and an E triad.

The notes above a seventh chord are called extensions, and they are nothing new: 9, 11 and 13 are simply degrees 2, 4 and 6 played an octave higher. The numbers just keep counting scale steps past 7. As intervals, the 9 is a major second an octave up, the 11 a perfect fourth an octave up, and the 13 a major sixth an octave up.

Start from the seventh-chord formulas you already know: C7 is 1 3 5 b7 (C E G Bb), Cmaj7 is 1 3 5 7 (C E G B), Cm7 is 1 b3 5 b7 (C Eb G Bb). Keep stacking thirds and the next three notes are always the 9, 11 and 13.

Extensions can also be altered, exactly like b3 or #4 in a scale formula: a b lowers the interval quality and a # raises it. The four alterations you will meet are b9 (a minor ninth), #9 (an augmented ninth), #11 (an augmented eleventh) and b13 (a minor thirteenth). Over C they are Db, D# (spelled Eb in practice), F# and Ab.

Upper structures have a shorthand: US plus a Roman numeral. US II means *a major triad built on degree 2 of the chord, played over the shell*. On C7, degree 2 is D, so US II is a D major triad (D F# A) over C E Bb.

The other way to write the same thing is a slash chord: D/C7, the triad on top, the chord underneath. Lowercase numerals (US iv) or m after the slash (F#m/C7) mean a minor triad.

To know what an upper structure sounds like, rename each note of the triad as a degree of the chord underneath. The triad's own 1 3 5 disappear; what remains are three degrees of the shell's root.

1. Write the shell: C7 = 1 3 b7 = C E Bb. C E Bb
2. Write the triad: D major = D F# A. D F# A
3. Name each triad note as an interval above C: D is a major second (a ninth, up the octave) = 9; F# is an augmented fourth = #11; A is a major sixth = 13. 9#1113
4. Merge: 1 3 b7 + 9 #11 13 = C13#11, full formula 1 3 5 b7 9 #11 13 (the 5 is understood even when nobody plays it). C13#11

Do the same for Ab/C7: Ab is a minor sixth above C = b13; C = 1 (doubling the root); Eb, heard as D#, is an augmented second above C = #9. So Ab/C7 = C7#9b13, formula 1 3 b7 #9 b13. Two triads, two completely different colours. The calculation is the same every time.

US II, a major triad a major second above the root, is the brightest and most common upper structure on a dominant chord. On C7 it is D/C7 = C13#11.

Put those seven notes in scale order and you get C D E F# G A Bb: 1 2 3 #4 5 6 b7, the lydian dominant scale (the fourth mode of G melodic minor). US II is that whole scale compressed into one chord. It sounds open and floating rather than tense, so it shines on dominants that do not need to resolve: a IV7 in a blues, a bVII7, a vamp.

When it does resolve, C13#11 pulls to F major: the #11 (F#) slides down a half step to F, the root of the new chord, and the b7 (Bb) slides down a half step to A, its third. Play the two chords and hear the two landings.

US bVI, a major triad a minor sixth above the root, gives the classic altered dominant. On C7 it is Ab/C7: Ab = b13, C = 1, Eb = #9, so the result is C7#9b13.

This is the dark, dramatic V chord. Both alterations lean downwards: the b13 (Ab) wants to fall to G, and the #9 (Eb) wants to fall to D, which is why US bVI is the natural choice when a dominant resolves to a minor chord. Notice there is no 5 in the formula: G and Ab sit a half step apart and would muddy the sound, so the shell leaves the fifth out.

Its close relative is US bIII, Eb/C7: Eb = #9, G = 5, Bb = b7. Result: C7#9, 1 3 5 b7 #9. This is the bluesy, rock-and-roll dominant: the #9 is the minor third rubbing against the major third E in the shell.

Two more major-triad structures bring in the b9. US bV is a major triad an augmented fourth (a tritone) above the root: Gb/C7. Gb = #11, Bb = b7 (doubling the shell), Db = b9. Result: C7b9#11.

It is tense but oddly symmetrical (C E Gb Bb plus Db lives inside the whole-tone and diminished worlds), and it is also the shape of a tritone substitution: the Gb triad is the top of Gb7, the chord that shares C7's E and Bb.

US bII is a major triad a minor second above the root: Db/C7. Db = b9, F = 11, Ab = b13. Result: C7b9b13 with an 11 in it, formula 1 3 b7 b9 11 b13. Be honest about that F: it sits right above the shell's E, so the chord is darker and more clustered than US bVI. Many players use US bII exactly for that grinding quality, and resolve it to a minor i.

Minor triads float over a dominant just as well, and they reach combinations the major triads cannot. The calculation is identical: rename the three notes as degrees of C.

F#m/C7 combines a b9 with the bright 13 and #11: the sound of the half-whole diminished scale (C Db Eb E F# G A Bb), where all those degrees live together. Bbm/C7 keeps the b7 and adds b9 and 11: with the 11 (F) leaning on the 3, it feels suspended and dark, a great sound on a dominant that is delaying its resolution. Dm/C7 is the gentlest: only natural extensions, 9 11 13.

A major seventh chord (1 3 5 7) accepts fewer colours than a dominant (the natural 11 clashes with the 3, and the b9 and b13 sound wrong), but three triads work beautifully. The shell is now C E B (1 3 7).

G/Cmaj7 is the warm, everyday Cmaj9. D/Cmaj7 stacks the whole lydian scale (1 2 3 #4 5 6 7) into one chord: modern, bright, the sound of film scores and neo-soul. Bm/Cmaj7 is the same lydian world with the 7 on top of the triad instead of the 13.

Over a minor seventh chord (1 b3 5 b7) the natural 11 is welcome, because there is no major third for it to fight, so minor chords take the plain, unaltered extensions. The shell is C Eb Bb (1 b3 b7).

Bb/Cm7 is the standard Cm11, the sound of a ii chord in jazz and of countless soul vamps. Gm/Cm7 is the softer Cm9: no 11, just 9 on top. F/Cm7 brings the natural 13 (A): that is the dorian colour (1 2 b3 4 5 6 b7), because natural minor would have Ab, a b13.

Put the three chord types together in the progression from the Cadences chapter: Dm7 G7 Cmaj7, a ii-V-I in C major. Each chord gets a shell in the left hand and a triad in the right. Because the triads are so small, they voice-lead almost by themselves.

Watch the right hand. From E A C to E A C# only one voice moves, and only by a half step. From E A C# to F# A D the A stays and the other two rise by a half step each: E → F#, C# → D. Three rich chords, and the right hand never moves more than a whole step.

For a darker V, swap in US bII: Ab/G7 (Ab C Eb = b9 11 b13). It resolves to the same D/Cmaj7, with Ab → A and C → D closing the gap by step.

Look once more at D/C7: C13#11, 1 3 5 b7 9 #11 13. Every idea in this course is inside that formula.

• 1 3 5: the triad (Triads chapter). C
• b7: the seventh chord, and the b that marks it as a dominant (Seventh Chords). C7
• 9 11 13: the scale degrees 2 4 6 an octave up (Major Scales, Intervals). 9 11 13
• #11: an alteration, the same #4 that turns major into lydian (Modes). #11C lydian
• The whole chord is a V looking for its I, or refusing to go there (Cadences, Secondary Dominants, Modal Interchange). C13#11 → Fmaj7

The major scale was the ruler; every chord was a selection of its degrees, sharpened or flattened. Upper structures simply let two hands share the ruler: a shell below, a triad above. The ear puts the pieces together.