Like much of the material on his previous two solo albums, Keep Movin' and Shakin' The Ground, Stepping Up is influenced by funk, soul and fusion and has unmistakably West Coast feel and a harmonic setting that would be quite at home in the work of Steely Dan or Stevie Wonder. As a result the progressions featured have an unashamedly 1970s tinge. The harmony utilised reminds me of the track 'Got My Feet Back On The Ground' by Peter Frampton, from his 1979 album 'Where I Should Be' featuring Tower of Power.
The song might be best termed multi-modal as it weaves its way through many key/mode changes and does so with a variety of techniques such as symmetrical and parallel changes, voice leading and backcycling that make it all seem completely effortless.
The verse is a two mode vamp based on F Dorian and then Db Mixolydian, it can be reduced in essence to just Fm7 moving to Db7. Both chords share a common tone, 'F'. It is probably easiest to think of this as a 'minor 3rd' move however since F Dorian is the second mode of Eb Major, while Db Mixolydian is the fifth mode of Gb Major; Eb and Gb are a minor third apart. The Db7 also feels like a substituted V7/V - try playing a C7 after the Db7 to return to the Fm7. Whatever your view, it sounds cool and though the verse is in essence 'static' it creates real motion and lift to the section.
There is a short connecting section between verse and chorus which I have avoided referring to as the pre-chorus but has a similar functional quality as it sets up a clear shift to a new key for the Chorus, Db Major, and does so with an backcycle using some augmented chords Bb+ (V/ii) leads to Ebm (ii), then Ab+ (V) leading to Db (I).
The chorus continues with Db as the tonic but borrows chords from Db minor (the minor iv and v, bVI and bVII Note; I have tried to use friendly chord names here on the scheme, so the bVII is enharmonically referred to as B13 and not Cb13 which is correct in Db). The bVI - v - iv section is used is a short repeating motif before navigating back to the verse via B13 (bVII), Cm7 (this is a surprise, straight to the v of F minor) and then Gb9, a tritone sub for C7 thus V7 back to i (Fm). The conclusion of the second chorus utilsies another minor 3rd transposition taking the bVII - v - iv progression up a minor third to become a distinctly new section all of its own for the guitar solo. This is a very similar idea to that featured in You are The Flower.
So, now we have an repeating vamp moving CMaj7 - Bm7 - Am7 - D13 and is therefore diatonic to C Lydian (fourth mode of G Major) which then flips to C Mixolydian with the Bb/C - C13 section. This is subsequently moved up symmetrically, by another a minor third, to Eb Mixolydian before the Gb9 returns us to the original vamp, and feel, in F Dorian.
The last chorus is identical to chorus two and uses the same structure but with one further twist in the outro in that following the C Lydian section we move UP to E Mixolydian and this idea moves back and forth four times before, on the 5th time, we follow the structure established in original solo -moving through C Mixolydian then Eb Mixolydian before an unresolved syncopated Gb9 concludes the track.
It is certainly complex to wade through the underpinning theory but regardless it is the sound that really matters, and this track sounds really great. Just playing the track and learning the chords will open your ear to a wide range of songwriting technique that, whether you are inclined to analyse it or not, will give you plenty of ideas for practice, improvising and composing.
Here's the songscheme or click here if you prefer a hi-res PDF version.
As ever, the accompanying video features all of the relevant sections as a guide..