A practical field guide to harmony

What this site is

modalinterchange.com is both an ear-training course and a reference for harmony in popular music, which means: rock, funk, blues, gospel, reggae, country, metal, soul, dance, folk, and hip-hop.

There’s one central idea: the main objects to study are modes. Most music theory textbooks and YouTube courses get into modes late, as a short chapter near the end. Here, we flip that. We instead study modes as the harmonic environments that songs live in.

Which mode you’re in determines:

• What the native chords are
• What kind of pull each chord has
• What kind of chord the home chord is — minor 7 in Dorian, dominant 7 in Mixolydian, major 7 in Ionian, etc.
• Which short chord loops (vamps) and resolving moves (turnarounds) are idiomatic

Popular music is “in a mode” essentially all of the time: either just one, or a blend of neighboring modes. Most of what makes a song’s harmony feel like something is which environment it’s in, how the song moves inside of it, and more often than not, how the song moves between environments, which is called modal interchange (hence the site’s name).

Mechanically, a mode is an ordered collection of pitches with a root note. 7-note modes are the most common form, and they’re the center of this pedagogy, but you’ll see 5-note, 6-note, 8-note, and 9-note modes sometimes too.

For each mode, there’s a set of lessons that cover its characteristic moves: what to listen for, what to try, and timestamped examples from real songs so you hear each move in a few different contexts. There are roughly 100 recurring moves among the core modes that form the fundamental vocabulary of chord progressions. If you learn all of them, you should have substantial working ear-training ability for popular music — not rules, but the actual musical building blocks trained into your ear.

Where to start

1. 1 Ready to play? Start with a two-chord Dorian vamp, i7–IV7. Grab an instrument or spin up a DAW and spend 15 minutes playing and listening to examples. This vamp is crazy common, the basis for so much great music, and as you play it you’ll start to hear why. The Dorian i7–IV7 lesson →
2. 2 Need the prerequisites? A quick primer on chords, scale degrees, roman numerals, and what “mode” means. Just enough theory to get started. Getting ready →
3. 3 Already know some theory? This site asks a different question — “what mode are we in, and where is this chord relative to the root chord?” — with six core modes, not two (major and minor). It’s a different foundation from classical and jazz theory, though it’s compatible with both. Worked examples throughout. How this is different →

Who this is for

It’s for musicians and music-makers of any kind — keyboard players, bass players, horn players, producers, singers, songwriters — anyone who wants to understand the music they listen to and play.

Modes appear late in most curricula, which makes them look like an advanced topic. But that’s a curriculum problem — they’re not inherently that complicated and they don’t require that much background. The bet here is that they can instead be taught early, as fundamentals.

You’ll need to know what a chord is, or be willing to spend 20 minutes to find out. And you’ll need a way to play short progressions (an instrument or a DAW). You do not need to read sheet music and you do not need perfect pitch.

There is a little bit of basic music theory that the lessons assume — everything you’ll need is in Getting ready for the mode lessons.

What you’ll get out of it

The goal of the course — and the research bet I’m testing — is that you’ll be able to hear the harmonic moves in real music, in real time, by name. You should be able to use them in your own music with intention.

The idea is that learning these fundamentals should kick off a compounding loop: you’ll start recognizing the vamps and turnarounds you study in the music you hear and play, and each one of these can become an ear-training rep, free and automatic. Being able to listen and harmonically analyze music in real time means you’ll get a LOT more volume than if you have to look up every song on Ultimate Guitar. Over time you’ll keep hearing each basic move in a ton of different contexts, and you should also be able to see harmonic patterns across your own taste.

If you play chords (even if your instrument is just Ableton), ear-training on these 100 moves should also improve your ability to harmonically improvise — that is, sit down and make a chord progression out of a felt sense of what should come next. And improvising this way also becomes a type of ear-training rep the more you do it.

Also: real-time harmony recognition feels great. It’s so cool. I can vouch for this method because this is what worked for me (I bought a piano in 2024 and started studying music theory seriously after 12 years or so as a casual musician). This site is the systematized version of what I taught myself.

To be clear: the fundamental 100 common moves don’t cover all harmonic possibilities. A song’s harmony can be very complex, and there is a long tail of harmonic possibilities (vamp combinations, substitutions, variants, unusual moves, ...), but the 100 are the fundamental pieces you’ll want in order to contextualize the long tail. Personally, even now, I can only follow the harmony of maybe 90% of what I hear. But this vocabulary also makes the other 10% approachable: when there’s a complex progression, I can usually hear some of the simpler moves it’s built from, and I know those moves from studying two-chord vamps.

There are roughly 100 recurring moves that form the fundamental vocabulary of chord progressions.

These days, I don’t just identify chord progressions — I can actually feel them. A ♭VI–V turnaround for example is something I feel first and foremost — before I name it, and even when the sound quality is bad and I can’t hear each instrument clearly (e.g. the song is playing in the distance, or over grocery store speakers). Each vamp and turnaround feels different. And this works in reverse too: when I improvise at the keyboard, I often get a felt-sense of where I want to go harmonically, and that sense translates into specific chords.

How this is different from other music theory

Beginner theory — “music theory for dummies” and so forth — focuses on the major and minor scale, which this site calls Ionian and Aeolian. (Beginner books often list three minor scales, but Aeolian — the “natural minor” — is the only one that really works as a home environment; the other two show up mostly as borrowed colors). Modes, when they’re introduced, are introduced as rotations of the major scale, e.g. “Dorian is the major scale starting on the 2nd scale degree” or “Dorian is the 2nd mode of the major scale”.

The first problem: that tells you how to spell Dorian, for instance, but not how to hear or inhabit it, and furthermore it suggests that Dorian is something that lives inside the major scale, rather than as an environment that exists on its own terms. The second problem is that many modes you’ll see are not rotations of the major scale at all (a notable example: Phrygian Dominant, which has its own set of lessons here).

This site uses parallel comparison instead. That is: different modes built on the same root. For instance: start playing in C major, then keep C as the root and start playing in C Mixolydian by lowering the B to B♭. Now you can hear directly what that change does to the environment.

University-level harmony courses teach a system based on what’s called common-practice-period music: the European classical tradition from Bach through late Romanticism. In this coursework, color is mostly organized by technique (for example: secondary dominants, chromatic mediants, augmented 6th chords) rather than by which mode the color comes from. I think it’s a good approach for that repertoire, but it’s a poor fit for the language of popular music.

Jazz theory has some powerful conceptual machinery, chord-scale theory especially. But chord-scale theory is primarily an improviser’s tool for navigating dense chord changes in real time: it answers the question, “what can I play over this chord right now?” This site asks, “where are we? and where is this chord relative to the root chord?” I study jazz improv myself and I use both approaches.

This site is organized around modal environments and modal interchange: the ways music moves between environments built on the same root note. It’s designed first for popular music traditions where songs usually keep the same root note for long stretches, and move within one environment or between neighboring ones built on that root. This is in contrast to other traditions where jumping between temporary key centers every few bars is part of the basic grammar — much of the standard jazz repertoire, and to a lesser degree, the classical repertoire. This site focuses on the recurring paths musicians use through and between modal environments, and it teaches that vocabulary with the goal of improving your ability to both recognize and create those paths in real time.

The longer version, with worked examples, is here: How this is different from other music theory.

Where the project stands

Also in progress: a full write-up of how key changes work from a modal perspective (tentative title: Orbital Harmony). This is an active research project in addition to being a teaching site; the mode lessons are an entryway into the larger framework.