How to analyze chord progressions
JTM008: My rule of 3 for harmonic analysis
Endless discourse
Harmony is possibly the most misunderstood and contentious subject among musicians. Whether in high school and college music theory courses, within bands discussing tunes, in the classroom with students, or the biggest battlegrounds of all–YouTube comment sections and Reddit threads—you’ll find endless discourse around harmony.
What I aim to do in this piece is provide a simple, practical framework for understanding chord progressions. This won’t fly in a college music theory classroom, but it will help the creative musician—one who improvises and composes—immensely in the practice room and on the bandstand.
Here’s my proposition: Every chord in a piece of tonal music can be grouped into one of three categories—a diatonic chord, a substitution, or a modulation.
Below you’ll find an outline for how I’ve learned to analyze chord progressions. Next week, I’ll be releasing the video essay of this piece as well as the full analysis of a piece of music using this framework. If you wish to support this publication and have these resources delivered directly to you, consider becoming a subscriber:
One thing—This piece does skip an important step, learning your basic keys, because there are already plenty of great resources for that and I felt it redundant to repeat. If you haven’t dug into this territory yet, I find this video from Andrew Huang to be especially informative and succinct:
Macro-Analysis & Micro-Analysis
There are essentially two ways to look at any piece of music: the full picture (macro-analysis) and the individual fragments (micro-analysis). The former allows for a broad perspective on the roadmap of a tune, while the latter investigates what a particular moment consists of.
When someone names the key of a song, they’re usually referring to macro-analysis. This often relates to where the song continually resolves. Macro-analysis would say the common key for the jazz standard Have You Met Miss Jones is F major. However, the bridge modulates to three other keys for brief moments. Still, the tune always resolves back to F major as well as at the end of the form.
Micro-analysis would say that the first measure of the bridge is in B♭ major, the second and third in G♭ major, the fourth and fifth in D major, and the sixth and seventh back in G♭ major—before resolving again to F major.
The framework I propose takes both views into account: the key of the moment and the key of the overall song. The key to both macro- and micro-analysis is this: a single chord gives you very little information. What’s essential is looking at what comes next—the progression.
The Rule of 3
Every chord in tonal music can be grouped into one of three categories:
A diatonic chord
A substitution
A modulation
Let’s take a deeper look into each of these categories:
Diatonic Chords
Diatonic means “within the key.” The tonic is the central tone—typically the name of the key (e.g., C is the tonic in C major). Calling a chord or progression diatonic means every note fits within the primary key.
A great example of a fully diatonic progression is Stand By Me by Ben E. King. The song is in A major, and the progression is A – F♯m – D – E. In Roman numerals, that’s I–vi–IV–V. Every chord contains only notes from the key of A, so the progression is entirely diatonic.
Substitutions
A substitution is a chord that’s related to the key but includes notes outside the key. While it might look like a key change at first glance, a substitution still functions within the primary key—it resolves back home.
Take Creep by Radiohead. It’s in the key of G major and uses this progression: G – B – C – Cm. This same progression also appears in The Air That I Breathe (The Hollies), Space Oddity (David Bowie), My Love Is Mine All Mine (Mitski), and likely many more.
Let’s break it down:
B (measure 2): This is a major III. It’s a parallel substitution for the diatonic iii (B minor), differing by just one note. Some also call it a borrowed chord from E harmonic minor, the relative minor of G major. B resolves to C, acting as a tension chord.
Cm (measure 4): This is a minor iv. It resembles the diatonic IV (C major) but with one altered note. In more formal terms, this could be explained as modal mixture—borrowing from the parallel G minor to add color. The progression from iv to I (Cm to G) is actually a type of cadence referred to as the plagal cadence (IV–I). Some even refer to iv–I as a perfect plagal cadence, though that term isn’t universal. Regardless, Cm functions as a substitution, adding tension before resolving back to G.
Modulations
A modulation is a true key change—a progression that resolves to a new tonic. Unlike a substitution, a modulation leaves the original key and stays in the new one (at least for a while).
This is something that most listeners can recognize in songs like Love On Top by Beyoncé or Stand by R.E.M. For me, one of the clearest modulations of all time happens right at the start of Wouldn’t It Be Nice by the Beach Boys.
The intro is in A major: A – F♯m – Bm – E – A – F♯m – C.
Then, the band enters in F major. That C chord is crucial. It’s not in the key of A, but that alone doesn’t make it a modulation. On its own, C could be analyzed as ♭III—borrowed from A minor. But what makes this a pivot chord is that it resolves firmly to the new tonic, F major, which remains the key moving forward.
Some key changes last only a few measures (like in Have You Met Miss Jones), while others last the rest of the song (as in Wouldn’t It Be Nice).
What’s next
Next week, I’ll be releasing a video essay version of this article, featuring an in-depth analysis of a song musicians have argued about for years: God Only Knows by the Beach Boys. It contains diatonic chords, plenty of substitutions, and a full-fledged modulation.
Until then—
Good luck, and happy practicing!