The Whole Picture, At Your Own Pace

The Circle of Fifths Tool: From Spinning Paper Dial to Something That Actually Talks Back

Why I built it

I've had one of those spinning paper Circle of Fifths dials for years. You know the kind — laminated card, plastic rivet in the middle, you twist the inner ring to your chosen key and it tells you the relative minor, the sharps, the flats, sometimes the diatonic chords if you're lucky. They're great. I'd recommend everyone owns one.

But they have a ceiling. A paper dial can show you the information — here are the seven chords in the key of G, here's where the relative minor sits — but it can't help you do much with that information. It can't show you what a I–IV–V actually looks like in twelve different musical contexts. It can't tell you that the same three Roman numerals power both a Chuck Berry shuffle and a Ramones single. And it definitely can't show you the chord shapes you'd actually reach for if you were playing it.

So this is the on-screen version, and it's been an excuse to push the idea a bit further than the paper one ever could.

The language of Roman numerals

Before getting into what the tool does, it's worth saying why Roman numerals matter, because that's really the whole point of the thing.

Once you know that the key of C contains the chords C, Dm, Em, F, G, Am, Bdim — and you know which is which by number — you've effectively learned something about every key. I–IV–V in C is C, F, G. In G it's G, C, D. In E it's E, A, B. The shapes change, the fingerings change, but the idea is identical. That's why a working musician can show up at a session, hear "it's a I–IV–V in B♭," and know exactly what to play.

The numerals also tell you the chord quality by their case. Capitals are major (I, IV, V). Lowercase are minor (ii, iii, vi). The little circle on vii° tells you it's diminished. So "ii–V–I" doesn't just mean "second, fifth, first" — it means a minor chord moving to a major chord moving home.

Speak this language fluently and you can transpose anything on the fly, communicate with other musicians without writing a note down, and start to hear why certain progressions feel the way they do. That's what this tool is trying to make easier to absorb.

What the tool does

Pick a key, see the chords

Top of the page, you pick a key. The twelve keys are laid out in circle-of-fifths order — C, G, D, A, E, B, F♯, D♭, A♭, E♭, B♭, F — same as the dial. As soon as you click one, the seven diatonic chords for that key appear, colour-coded by quality: green for major, amber for minor, a muted purple for the diminished vii°. Each chord is labelled with its Roman numeral underneath, so the connection between "the third chord in C major is Em" and "iii is a minor chord" is right there in front of you.

That alone is more useful than the paper dial, because seeing all seven at once — with their qualities and their numerals — is how you start to internalise the pattern. The pattern is the same in every key. That's the thing worth knowing.

Style cards: same theory, different accents

This is the bit I'm most pleased with. Below the chords, you get a grid of style cards — Pop, Blues/Rock, Jazz, Soul/R&B, Folk/Country, Neo-Soul/Indie, Reggae, Classical/Film, Grunge/90s Rock, Punk.

Each card shows a progression that's a signature of that style, written in Roman numerals so you can see the underlying logic, and then a couple of well-known songs in the selected key that use that progression. So if you've picked the key of G and you're looking at the Pop card, you'll see I–V–vi–IV with Wonderwall and Fast Car listed underneath. Switch the key to E and the same I–V–vi–IV is still there — but now the songs are Mr. Brightside and Yellow.

The point is to make the abstraction concrete. It's the same four-chord move every time. Oasis, Tracy Chapman, The Killers, Coldplay — all leaning on the same skeleton, just transposed and dressed differently. The Roman numerals are the bones; the song examples are the flesh.

You can also see, side by side, that Punk and Blues/Rock share I–IV–V (it really is just the tempo and the distortion that separate them), or that Pop's I–V–vi–IV and Reggae's I–V–vi–IV are the same four chords — the rhythm and the offbeat skank do the rest of the work.

Filterable chord voicings

Each style card has a row of tabs across the bottom: Open, Barre, Power, 7ths, Sus / Add, Ext, Triads. Click any of them and the actual chord shapes for that progression appear as fretboard diagrams.

This is the bit that the paper dial simply cannot do, and it's where I think the tool earns its keep. If you're working on a Folk/Country progression, the Open tab gives you the cowboy chords you'd actually use — first-position C, G, D shapes that ring out. Switch to Barre on the same progression and you get the movable shapes you'd want for playing higher up the neck or in keys that don't sit nicely open. Hit Power on the Grunge card and you get the two-note shapes you'd use for chugging downstrokes; hit 7ths on the Jazz card and suddenly you've got the maj7s and m7s that make ii–V–I actually sound like jazz.

The same I–V–vi–IV in G can be played as cowboy chords for a campfire singalong, as barre chords up at the seventh fret for a tighter pop sound, or as power chords for a punk version. Same theory, different application. Which is the whole reason any of this is worth learning.

By default no shapes are shown — you have to pick a tab. That's deliberate. The page would be a wall of fretboard diagrams otherwise, and the point is to let you choose which lens you're looking through.

Left-handed players: a quick word

Top right of the tool you've got an L / R toggle that flips every chord diagram, and a dark mode button. Hit Save as default and your handedness, theme, and last-selected key will be remembered the next time you load the page.

On the L / R toggle: as a lefty player myself, every tool on this site has been built with left-handed players just as much in mind as right-handed ones — and in some cases, primarily with us in mind. The default is right-handed simply because that's what most players are, but that's a default, not a hierarchy. Hit the L button, save your preference, and the tool will remember that's how you want to see things from then on.

The rest of the guitar world has a tendency to treat left-handed players as an afterthought — a footnote, a special order, a "you'll have to flip the diagram in your head." This site doesn't. Practice Room is just as focused on left-handed players as right, and the toggle is there to make that practical, not to tick a box.

How to use it for actual practice

A few things I've found it useful for:

Learning the diatonic family. Pick a key you don't know well. Look at the seven chords. Play them in order — I, ii, iii, IV, V, vi, vii° — and listen to how each one sits in the key. Do that in three keys this week and you'll start to feel the pattern rather than think about it.

Understanding what songs you already know are doing. Recognise the chords in Don't Stop Believin'? Look at the Pop card in F. That's the I–V–vi–IV move. Now you know one progression and one song that uses it. Click another key. Different song, same move.

Getting unstuck on voicings. You know a progression in open chords but want to play it higher up the neck — switch the filter to Barre or 7ths and there's a working version waiting for you. Or you know it as power chords and want to soften it for a quieter section — switch to Open or Sus / Add.

Transposing. You learned a song in G but the singer wants it in B♭. Change the key, look at the same style card. The shapes update, the numerals stay the same.

It's not a replacement for putting the work in. But it's a faster way to see the connections than flipping through a theory book — and considerably more useful than the spinning bit of card I've been carrying around for the last decade.

Pick a key. Have a poke around. See what falls out.