Diminished chords and scales have a reputation for being tricky — theoretical, pattern-heavy, and difficult to make sound musical. John Stowell’s approach cuts straight through that reputation by anchoring diminished sounds in something you already understand: dominant chords. Once you hear it that way, the whole system opens up.
What you’ll get out of this lesson
John guides you through the practical logic of diminished chord soloing, explaining how diminished chords function as dominant chords with a flat nine, and giving you a framework for choosing which of four possible keys to solo in over any diminished chord in a progression.
The Core Insight: Diminished as Dominant
The central idea John introduces is this: a diminished chord, in most harmonic contexts, can be treated as a dominant chord with a flat nine. Take an A-flat diminished voicing — the notes it contains are also present in a G7 flat nine chord. Because any diminished chord moves symmetrically in minor thirds, that same diminished chord is simultaneously A-flat diminished, B diminished, D diminished, and F-sharp diminished. And a half step below each of those roots sits a dominant chord: G7, B-flat 7, D-flat 7, and E7. So any single diminished chord gives you four potential dominant chord interpretations to solo from.
Choosing the Right Key in Context
With four possible dominant keys available, the question becomes which one to choose. John’s answer is simple: look at what comes before and after the diminished chord in the progression. Most of the time, one of the four keys will fit the surrounding harmony far more naturally than the others. He describes four common scenarios where diminished chords appear in progressions — including chromatic passing motion (as in classic tunes like “Ain’t Misbehavin'”, moving F major to F-sharp diminished to G minor) — and in each scenario the context makes the key choice clear.
Don’t be intimidated by the theory, but just grab a little piece of it that you can apply to your playing. Think about music as adding small chunks of information into your vocabulary in a way that’s comfortable for you.
Getting Past the Patterns
John is candid about the main trap with diminished scales: because they’re symmetrical, they’re very easy to play as patterns — half-step whole-step sequences running up and down the neck, or melodic shapes moving in minor thirds. These patterns are fine to practise for fretboard awareness, but they don’t sound like melodies. John’s solution is to treat the diminished context as a dominant context, which immediately gives your melodic language a tonal centre to resolve to, and makes it far easier to phrase musically rather than mechanically.
Chord Voicings and Voice Leading
John also demonstrates how diminished voicings can be combined with other chord types — major triads with a flat nine in the bass, diminished major seven voicings (replacing one note to add a major seventh), and simple triad-over-bass-note combinations — to create sounds that are less predictable than straight diminished patterns. Moving these voicings in minor thirds gives you a vocabulary of colours to play with both as a soloist and as an accompanist.
Taking it further
John mentioned in this session that he has a PDF resource of around seventy pages — including original tunes, chord melodies, magazine articles, and transcribed solos — that he makes available to students. If you’d like a copy, reach out via the details shared during the masterclass. Pairing this theoretical framework with John’s transcribed material is one of the most direct routes to hearing how these ideas sound in a real musical context.
Your homework
Find a standard that uses a diminished passing chord — “Ain’t Misbehavin'” is a perfect starting point. Identify which of the four dominant keys fits the context of that specific diminished chord in the progression. Then improvise over just that chord using the corresponding dominant vocabulary (a mixolydian scale or a ii–V lick in that key). Record yourself so you can hear whether it sounds musical or mechanical — and adjust accordingly.