THERE’S A TRICK USED BY MUSICIANS when they get lost: it’s called the cycle of fifths. It’s a kind of satnav device that allows you to get back home from just about anywhere. You can jump to any chord, for dramatic effect, and get back to where you started using a simple but effective technique.
The technique relies on the fact that in every key, there’s a special chord known as the dominant seventh that naturally leads you back to the root chord—the chord that is the basis of that key. Here’s the reason why it works.
Let’s say you’re playing in the key of C. The scale of C can be played entirely on the white notes of a piano, and that makes it the easiest key to play in.
The two chords ‘nearest’ to C are not B and D, but G and F. That’s because the scale of G has just one sharp, which makes it similar in sound to C – it shares most of the same notes.
Equally close, but in the other direction, is the scale of F. This has just one flat. Once again, this key shares all but one of its notes with C. You can see why this is the case here.
G is known as the dominant chord of C, and F as the subdominant. If you play the chord of G, and add the note F natural (not F sharp) at the top, you get the G7, the dominant seventh, so called because F is the seventh note in the scale of G. (Just to be confusing, the note F sharp is called the Major 7th.)
Each key has its dominant seventh – the seventh of the chord five notes higher than the root. If you play any dominant seventh, the listener naturally expects to hear the chord five notes lower afterwards.
This means that you can jump to a wildly different chord, and bounce your way back home by playing one dominant seventh after another, until you get back to where you started.
The best example I know is in the theme for The Flintstones. You can listen to it here, and the main tune starts when the singers begin. The music is in C, but jumps to E in the middle eight. The key of E has four sharps, so it sounds a long way from C. That’s why it’s such a strong chord to go to.
In fact, the song jumps to E7. And E7 just happens to be the dominant seventh of the key of A, which has three sharps, so the listener naturally expects A to come next.
Except that the chord that comes next isn’t plain A, but A7. And A7 is the dominant seventh of the key of D, which has two sharps.
Once again, though, the chord played isn’t D, but D7; D7 is the dominant seventh of the key of G, which you’ll remember has just one sharp.
By substituting G7, which is the dominant seventh of C, the tune naturally gets back to the root.
You can see the cycle in the third line of the score below.