The Jazz Chords That Made Steely Dan Sound Like Steely Dan

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You know a Steely Dan song within the first few seconds. There’s something about the sound—the sophistication, the smoothness, the hint of underlying unease—that immediately identifies it.

That signature sound comes primarily from harmony. While most pop songs use three or four basic chords, Steely Dan songs deploy extended chords, chromatic voice leading, and harmonic substitutions that would make a jazz musician smile.

This isn’t an academic exercise. Understanding these techniques reveals why their music feels the way it does—and might inspire your own compositions.

Extended Chords: The Foundation

Most rock music lives in triad territory: major and minor chords with three notes. Steely Dan extended chords add seventh, ninth, eleventh, and thirteenth intervals, creating richer, more complex harmonic colors.

Take “Deacon Blues.” The opening progression moves through:

Bm7 → A/B → Gmaj7 → F#7sus → F#7 → Em7 → Dmaj7 → C#m7 → F#7

Every single chord is an extended chord. No basic triads. The B minor starts as a minor seventh. The F# chord starts suspended before resolving to dominant seventh. Even the D major appears as a major seventh.

These extensions matter sonically. A major seventh chord has a dreamy, slightly unresolved quality. A dominant seventh chord creates tension that wants to resolve. Minor seventh chords feel melancholic but stable.

Modal Interchange: Borrowing From Parallel Worlds

Here’s where Steely Dan gets really interesting. They frequently borrow chords from parallel modes—essentially treating major and minor as fluid rather than fixed.

In “Peg,” the song is in G major. But listen to the pre-chorus:

G → Bm → C → D → Bm → C → Gm

That final G minor chord is the giveaway. In the key of G major, you’d expect a G major chord. The minor version borrows from G minor (the parallel minor key), creating a sudden emotional shift. The brightness of major turns melancholic.

This technique—modal interchange or modal mixture—appears constantly in their work. “Josie” borrows from parallel modes. “Aja” shifts between modes so fluidly the home key becomes ambiguous.

Tritone Substitutions: The Secret Sauce

Jazz musicians use a harmonic device called tritone substitution to create smooth bass lines and surprising harmonic colors. Steely Dan deploys this constantly.

In traditional harmony, a dominant chord (like G7) resolves to its tonic (C). The tritone substitution replaces that dominant with a dominant chord whose root is a tritone (three whole steps) away.

So instead of G7 → C, you might hear Db7 → C.

The two dominant chords share the same tritone interval (F and B, or B and F depending on spelling), so they function similarly. But the bass moves by half-step instead of fifth, creating a chromatic descent that sounds sophisticated.

In “Kid Charlemagne,” the bridge section uses tritone substitutions to create descending chromatic bass lines that feel inevitable yet surprising:

F#7 → B7 → E7 → A7 → Dmaj7

Each dominant chord could resolve to its expected tonic, but instead moves to another dominant, delaying resolution until finally landing on D major.

The Mu Major: Steely Dan’s Signature Chord

Donald Fagen has specifically mentioned their use of what they call the “mu major” chord—a major triad with an added second (or ninth) replacing the third.

A C mu major would be spelled: C - D - G

This isn’t a standard chord symbol because it doesn’t fit traditional harmony theory. It has a major quality (due to the fifth relationship between root and fifth) but avoids the defined major/minor third that gives chords their emotional character.

The result is ambiguous, floating, slightly mysterious—perfect for Steely Dan’s lyrical themes of deception and moral ambiguity.

You’ll hear mu major chords throughout their catalog, often voiced on electric piano or guitar. They contribute significantly to that “Steely Dan sound” that other artists struggle to replicate.

Slash Chords: Bass Line as Composition

Slash chords (chords with specific bass notes indicated, like C/E) appear throughout Steely Dan’s work. These aren’t just inversions for voice-leading—they’re compositional elements.

In “Hey Nineteen,” the verse progression uses slash chords to create a descending bass line:

Dm7 → C/E → Fmaj7 → G

The bass descends: D → C → F → G. The chords above change, but that descending motion creates momentum and direction.

This technique—using the bass line as an independent melodic element while chords shift above it—is straight out of classical composition and jazz arranging. Steely Dan applied it to pop songs.

The Result: Accessible Complexity

Here’s the remarkable thing: despite all this harmonic sophistication, Steely Dan songs remain catchy and accessible. You don’t need to understand tritone substitutions to enjoy “Peg.” The complexity operates below the surface, adding depth without demanding analysis.

This is the ultimate lesson from their harmonic approach: complexity and accessibility aren’t opposites. Listeners can appreciate sophisticated music on multiple levels. Some will just enjoy the groove. Others will analyze the chord substitutions. Both experiences are valid.

Walter Becker and Donald Fagen were music school students who loved jazz, blues, and pop equally. They refused to choose between intellectual rigor and commercial appeal. Their harmonic language reflects that refusal—jazz chords in service of pop songs, complexity that invites rather than excludes.

The next time you hear that unmistakable Steely Dan sound, listen for the extended chords, the modal borrowing, the chromatic bass lines. They’re the harmonic fingerprints of two songwriters who decided that popular music deserved better than three-chord simplicity.

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