Not Too Much states its home key by hiding its root. The rhythm guitar alternates two upper-voice triads in first inversion, B-flat over D and A-flat over C, the major third of each chord set as the lowest sounding pitch. The bass guitar stays out for four bars, so that guitar third is the actual floor. In A-flat major the move reads as a two chord in first inversion easing to a one chord in first inversion.
The song holds its root back on purpose. When the bass finally enters at bar three and a half on A-flat, rooting the home chord on the downbeat of bar four, the identity commits for the first time. The four-bar delay keeps the harmonic floor floating, neither chord planted on its own root. The opening is the song refusing to land until it chooses to.
The main engine of the song rocks two sus chords a whole step apart, B-flat-sus4 and A-flat-sus4. The bass walks under both, B-flat then A-flat, with quick chromatic approach tones brushing through on the way. The rhythm guitar voices each side as a sus, root and fourth and fifth, no third in either, so neither chord commits to major or minor. The two chords trade with no dominant between them, a flat-side rock instead of a functional cadence.
The seam between the two chords is the interesting part. A-flat is the flat-seven of B-flat and the root of the next chord at the same time, one pitch belonging to both. The rocker turns on that shared tone, the harmony rocking a whole step with a common thread holding it together. The song keeps its motion small and its center loose, two chords doing the work of a whole progression.
The chorus holds a B-flat and slips a chromatic C-sharp through it. The rhythm guitar plants a B-flat bed, B-flat and F and B-flat, then alternates a C-sharp voicing into it, C-sharp and A-flat and C-sharp, the C-sharp the enharmonic D-flat that the chart called the song's D-flat field. That chromatic C-sharp is the bite of the chorus, a half-step rub leaning against the held B-flat. Around it the guitar brushes a brief E-flat and C and A-flat before settling back on the B-flat.
Over the held floor the voice comes down. It descends C-sharp to C to B-flat to A-flat, a step down through the chromatic and into the home tones, then lifts back and parks on a held whole-note B-flat as the harmony shifts under it. The chromatic C-sharp in the guitar and the descending vocal share the same half-step bite, the line falling through the rub the chord keeps ringing. The chorus is a held B-flat colored by a chromatic C-sharp, the voice settling onto the 9 rather than reaching past it.
The verse cycles the same two sus chords a whole step apart, B-flat-sus4 and A-flat-sus4, both with no third, the bass walking under both. The rhythm guitar stacks each as root and fourth and fifth, neither one committing to major or minor. Quick sixteenth-note approach tones brush past as the bass moves. The harmonic bed is the rocker, steady and flat-side, the same engine as the main.
The voice enters on B-flat, the root of the first chord, then slides down to A-flat, the flat-seven of B-flat. Under the A-flat chord the line descends through E-flat and G and F, all diatonic to A-flat major. The G is the major seventh, the most expensive interval in the key, and the F is the sixth, the song's home-but-not-quite tone. The singer carries "It's more than make believe, there's things I can't unsee" across that descent.
The bridge holds the song's central flip and the band drops the bass to underline it. For eight bars the rhythm guitar alone carries the chords. It opens on C over E, a C major triad with the major third in the bass, then lifts to A-flat-add-nine and B-flat-add-nine, both bright. The floor stays guitar-only, with no low end to confirm anything.
Then the trick arrives. The rhythm guitar plays both E-natural and E-flat in the same measure, flickering between C-over-E and C-minor-over-E-flat, major to minor on the same root. The whole shimmer turns on which third the strummer picks up next. The bass holds off before it enters it, and the major-or-minor question stays open until the chorus reprise walks the floor back to A-flat.
The song lives in the A-flat field through the verses and the chorus. The outro refuses to go home. The bass walks chromatically downward, A-flat to E to E-flat to D, and the rhythm guitar plays four-note clusters that tighten each bar, the E lowering to E-flat as the bass descends. The texture closes in instead of opening out.
On the final bar the rhythm guitar opens to a clean D-major triad and the song stops there. D is a tritone from A-flat, the chord most foreign to the home key, and the song does not walk back to it. The title gets stated in harmony at the close, not too much resolution, no plagal cadence, no return to the home chord. The song halts a tritone away from where it started.