The Cycle of Fifths is the key to understanding Western music. It is truly a thing of beauty in its symmetry, simplicity and fruitfulness. As a Classic Guitarist, the cycle of fifths has taught me a great deal about harmony and transposition. But whatever your instrument, learning the cycle of fifths is time very well spent.

Conventionally, the cycle of fifths is introduced by first discussing major scales in all keys. This is the keyboard harmony approach. But for guitarists, I think it's easier to come at it directly - first create the cycle, then see what we can do with it.

Imagine a clock face.

Where the 12 would be, write the note C.

Where the 1 would be, write the note G which is a perfect fifth above C.

Where the 2 would be, write the note D which is a perfect fifth above G

Continue by fifths - A, E, B, F#, C#, which takes you to 7 o'clock.

Now go back to the top and this time go anticlockwise

Where the 11 would be, write the note F which is a perfect fifth below C

Where the 10 would be, write the note Bb which is a perfect fifth below F

Continue by descending fifths - Eb, Ab, Db, Gb, Cb

Now look at what you've created:

We created the cycle by thinking of notes, but let's now think of it in terms of major keys. Starting with C which has no sharps or flats, clockwise we go through progressively sharper keys. G has one sharp, D has two, A has three, and so on, with C# having the maximum seven.

Again starting from C, anticlockwise we have the sequence of flat keys. F has one flat, Bb has two, Eb has three, and so on, with Cb having the maximum seven.

Because we nowadays use Equal Temperament tuning on keyboards and guitars, F# and Gb are exactly the same pitch, as are C#/Db and B/Cb. (I explain this in detail in my Equal Temperament Guitar Tuning page).

Using the Cycle

Most guitarists are familiar with the Three Chord Trick used for accompanying hundreds of simple songs. Playing in C, you need the chords F and G. But F and G appear one step anticlockwise and clockwise from C in the cycle. This is true for every key. For example, to play in Ab, you'll need Db and Eb, the adjacent chords.

Then, playing in C, you'll often need Am (the relative minor of C). In the cycle of fifths, the relative minor is always three steps clockwise round the cycle. So, in our Ab example, you'll need Fm.

These are simple examples, but the beauty and power of the cycle lies in its perfect symmetry. Though we started with C at the top, thanks to the ingenuity of Equal Temperament, the circle is complete and relationships between keys hold good at every point.

Making a Transposing Tool

A useful transposing tool (mostly for guitarists) can be made from two cycle charts, one smaller than the other, pinned together at the centre so that they can rotate. See below:

Suppose you have a chord sequence for a song, like this:

Cm / G / | Cm / Bb / | Eb / / / | G / G7 / |

(which is the start of St James's Infirmary, in Cm)

If you want to play it in Fm, rotate the inner disc till the C lines up with the F on the outer disc. Then simply read off the new sequence. The sequence of majors, minors, sevenths etc doesn't change. Only the letter name changes:

Fm / C / | Fm / Eb / | Ab / / / | C / C7 / |

This is a relatively simple transposition into a closely related key, and many players could do it 'on the fly'. But for more remote key changes, or sometimes for arranging on paper without an instrument handy, the transposing tool can be a great help.

Finally, this was intended simply as an introduction to the cycle of fifths. At the risk of sounding mystical, the more you look into this beautiful structure, the more insights it will give you into how music works.