Circle of Fifths

The circle is an answer to a practical question: given a key, what belongs to it and where can it go next. The wheel puts every major key in fifth order, pairs each with its relative minor, and makes the signature visible as distance from C. This page adds sound to that map, so a key signature is not only read but heard.

#What the wheel encodes

Moving clockwise from C goes up by perfect fifth: C, G, D, A, E, B, then the enharmonic middle of the circle, then the flat side back toward F. Each clockwise step adds one sharp to the signature. Moving anticlockwise goes down by perfect fifth and adds one flat. Neighbouring keys share six of their seven diatonic notes, which is why the wheel is also a first estimate of easy modulation targets.

The inner ring uses the same order for relative minors. A relative minor starts on the sixth degree of its major key and uses the same signature with a different centre: A minor for C major, E minor for G major, D minor for F major. The spelling switch chooses sharp or flat names where both exist, at B and Cb, F# and Gb, and C# and Db.

#Reading a signature without counting lines

Sharp signatures accumulate in the order F#, C#, G#, D#, A#, E# and B#. Flat signatures accumulate in the order Bb, Eb, Ab, Db, Gb, Cb and Fb. The readout states the count and names the accidentals, so the signature can be checked against a staff: D major has two sharps, F# and C#, while Bb major has two flats, Bb and Eb. For a minor key, the signature belongs to the parent major, but the centre is the tonic shown in the readout.

Parallel majors and minors share a tonic but not a signature. C major has no sharps or flats; C minor has three flats. That distinction matters because players sometimes confuse parallel with relative. Relative means the same notes with a new centre. Parallel means the same centre with changed notes.

#Hearing the chords that belong to a key

The chord panel lists the seven diatonic triads with roman numerals, or the seven diatonic seventh chords when sevenths are selected. Clicking a chord plays it in a compact voicing, names its notes, and marks those notes on the keyboard. The scale stays highlighted underneath, so the chord is seen as a selection from the key rather than an isolated shape.

Use the panel to compare functions across keys. Play I, IV and V in C, then move one step clockwise and play I, IV and V in G. The shapes change, but the relationship does not. Then switch to sevenths and listen for the added tension in V7 and the softer colour of Imaj7. If a chord sounds wrong for the label, check the note pills before assuming the tool is wrong: most errors come from expecting a raised leading tone in minor, which belongs to harmonic minor rather than the natural-minor diatonic set used here.

#Choosing where to go next

Start with the neighbours. From C major, G major adds F# and F major adds Bb. Those are the closest modulation targets because only one note changes. The relative minor is closer still in one sense, since no note changes, but the centre moves from C to A. The parallel minor is a stronger colour change because the signature moves from no sharps or flats to three flats.

Three checks work well. First, transpose a short loop such as I, V, vi and IV into the key one step clockwise and listen for the altered note. Second, compare C major with A minor by playing the same chords and attending to where each phrase wants to rest. Third, when a piece contains a chord outside the key, look at the neighbouring key that contains it; the wheel often identifies whether the chord is borrowed, a secondary dominant, or the start of a modulation. For timing work while doing this, the metronome keeps the loop steady, and for interval checking the ear training studio uses the same sound engine.

#What it leaves out

The wheel describes diatonic major and natural-minor harmony. It does not generate secondary dominants, borrowed chords, chromatic mediants, blues inflections, or tuning systems. Those are real and common, but they sit outside the map. In minor keys this page uses the natural-minor v chord; much minor-key music raises the seventh to make a major V, especially at cadences. That raised leading tone is a chromatic alteration, so it is mentioned here as a boundary rather than included as a diatonic chord.

Enharmonic spellings are also a notation choice, not a sound difference in equal temperament. F# major and Gb major sound the same on this page; they differ in how the notes are named and how the signature is written. The sharp and flat switch controls that naming, including the less common but correct extremes: B major with five sharps against Cb major with seven flats, F# major with six sharps against Gb major with six flats, and C# major with seven sharps against Db major with five flats.