Think You Know All the Chords in C Major? Think Again.

You’ve probably been told that in C major, the chords are:
Cmaj7 – Dm7 – Em7 – Fmaj7 – G7 – Am7 – Bm7♭5.
Boom, that’s it. All done. Game over.

But let me ask you—if I threw an E♭min7 or A♭maj7 into a tune in C major, would you know why it sounds so good? Would you know where it’s going, and more importantly, how to use it in your own playing?

This post is all about breaking past the basic diatonic chords and diving into the real harmonic universe that surrounds C major. Get ready to explore secondary dominants, 2-5’s, tritone subs, modal interchange—and how they all help you sound more sophisticated, musical, and downright jazzier.

The First Expansion: Secondary Dominants

Let’s start with something you’ve definitely heard, even if you didn’t know what it was called: secondary dominants.

You’re playing in C major, and all of a sudden, you hear a D7 chord. Wait a second—D7 isn’t in C major! But it sounds great. Why?

That’s because it’s a V of V. D7 wants to resolve to G, which is the dominant in C. That makes it a secondary dominant—a dominant chord temporarily borrowed from another key, just to push us toward a new chord more strongly.

Here’s how this works in C major:

• A7 → Dm7 (A7 is V of ii)

• B7 → Em7 (B7 is V of iii)

• C7 → Fmaj7 (C7 is V of IV)

• D7 → G7 (D7 is V of V)

• E7 → Am7 (E7 is V of vi)

• F7 → Bm7♭5 (F7 is V of vii)

Boom—six new chords, just by adding secondary dominants before each diatonic chord. And the best part? They sound great in a jazz context.

Let’s Double the Fun: Secondary II-V’s

Now that you’ve added those dominant chords, you might be thinking—“Wait, what about the ii that usually comes before a V7?”

Great question. Let’s add secondary ii-V’s to the mix.

For example:

• To get to Dm7, instead of just playing A7 (V of ii), we now do Em7♭5 → A7 → Dm7

• To get to Em7, we do F♯m7♭5 → B7 → Em7

• To get to Fmaj7, it’s Gm7 → C7 → Fmaj7

You’re now adding both ii and V before your target chord. This creates smoother transitions and richer harmonic movement. This technique alone is found in hundreds of standards, from Stella by Starlight to All the Things You Are.

Enter Tritone Substitutions

Time to turn up the chromaticism even more.

Remember that every dominant chord (like G7) has a tritone sub—a chord a tritone away that shares the same tritone interval and voice-leading tendencies. So instead of G7, try playing D♭7. Now things are sounding spicy.

Examples:

• A7 → Dm7 becomes E♭7 → Dm7

• D7 → G7 becomes A♭7 → G7

• You can even mix and match: ii → tritone sub → destination

This is where jazz players like Wes Montgomery and Bill Evans really start to play with “harmonic plumbing”—still getting to the same harmonic destination, but taking more interesting roads to get there.

Borrowing From the Parallel Minor (a.k.a. Modal Interchange)

Let’s say we’re still in C major, but you hear an A♭maj7 pop up out of nowhere. It’s not in the key, but somehow it works. Why?

That’s because it’s borrowed from the parallel minor—C minor.

The chords in C minor come from E♭ major (its relative major), which gives us:

• E♭maj7, Fm7, Gm7, A♭maj7, B♭7, Cm7, Dm7♭5

You can borrow any of these and toss them into your C major progressions. Think of tunes like Christmas Time Is Here or Girl From Ipanema—they’re packed with chords like A♭maj7 or B♭13 that enrich the harmony without abandoning the home key.

Modal Interchange and Beyond

Let’s go even further.

Every mode—Dorian, Lydian, Mixolydian, Phrygian, and even melodic minor variants—offers a new set of chords you can borrow from, as long as you keep the tonal center clear.

For instance:

• C major → borrow from C Dorian (think B♭ major chords)

• C major → borrow from C Lydian (use D major-type sounds)

• C major → borrow from C Mixolydian (use chords from F major)

This gives you new textures and colors that are technically chromatic but feel totally at home—if you use them with intention.

So How Many Chords Are We Up To?

We started with 7 diatonic chords in C major. Now, by layering:

• 6 secondary dominants

• 6 secondary ii chords

• 7 chords from the parallel minor

• Several tritone subs

• Modal interchange options

...we’re way beyond 25 chords that can function within the key of C major.

And we haven’t even started looking at what happens when you apply these ideas to modulations, deceptive resolutions, and other advanced substitutions. But don’t worry—we’ll get there.

The Big Takeaway

These aren’t just random jazz tricks. Every chord you add must have direction—it needs to lead somewhere.

That’s the true secret: understanding where the chord wants to go, not just naming it.

If you’re still unsure how to use these ideas in tunes, I’ve got a free guide in the Jazz Guitar Accelerator or you can join the Jazz Guitar Fellowship. We go through five to ten jazz standards step-by-step and cover how to actually use these chords in context.

Cheers,
Marc
JazzGuitarLessons.net