Compatible chords
Choose a chord: the other chords that naturally work with it in the same key are shown below, grouped by harmonic degree.
This tool answers a very concrete question: once you've picked a chord to start a song, which other chords can you pair it with without stepping outside the key? It's for anyone writing or improvising a progression who wants to avoid picking chords at random, just as much as for anyone learning theory who wants to see, on a real example, what "staying in key" actually means. The result sorts compatible chords by degree (I, ii, iii, IV, V, vi, vii°) rather than as a flat list — that ordering is what tells you which chords sound stable, which create tension, and which one naturally resolves back to the tonic. What you gain is a reliable base for building your own progressions, without having to memorize key theory first.
The diminished degree (°) has no diagram: it's rarely played in that exact form, and the site only shows chord fingerings that have actually been verified. Its name is still shown for reference.
How the degree ranking works
Every major or minor key is built on seven notes, and each of those notes carries its own chord: three major, three minor and one diminished, always in the same relative order regardless of the starting key. Picking a starting chord in the selector is really telling the tool the likely key of the song — it then works out the other six chords of that key and displays them sorted by degree, from I (the tonic, the "resting" chord) to vii° (the diminished degree, the most tense).
This relationship between the seven chords has a name: diatonicism. A "diatonic" progression is built entirely from chords of the same key — it's the most common structure in popular music, well before you even start thinking in terms of cadences or harmonic tension. Deliberately stepping outside that list (borrowing a chord from another key) is possible and even common, but it's not something this tool calculates automatically: it shows the diatonic base, not the borrowed chords.
Practical tips and common mistakes
- Don't treat the seven degrees as interchangeable: the I, IV and V carry most of the harmonic weight in most styles, while the other degrees (ii, iii, vi) mostly serve as variation or transition.
- The vii° (diminished) degree is rarely played as-is in popular music — it mostly works as a theoretical reference point. In practice, many songs avoid it or substitute a neighboring chord instead.
- A "compatible" chord isn't a mandatory one: diatonic compatibility guarantees no note will clash, not that a progression will sound interesting. Your ear is still the final judge.
- If a chord on the list sounds off in your context, check the starting chord you picked first: a misidentified key throws off the entire ranking that follows.
- To visualize the same logic from a different angle — which keys are "neighbors" of one another, rather than which chords make up a single key — the circle of fifths pairs well with this page.
Concrete example
Take C major as the starting chord: the seven diatonic degrees are C (I), Dm (ii), Em (iii), F (IV), G (V), Am (vi) and B° (vii°). The C – Am – F – G progression, extremely common in pop, only uses degrees I, vi, IV and V — that exact core of three major chords and one minor is what keeps coming back across countless songs, in different keys but with the same degree logic.
Once that logic clicks, it transposes directly: the same I–vi–IV–V progression in G major gives G – Em – C – D. To build and hear this kind of progression directly, the generator applies this same degree logic interactively: