The Key Cycle
There are many reasons why you need to be able to play equally well in every key. Bands often have to play in keys that suit their singer. That could be F# or Db for example. E and A are common keys for guitar, while horn players like flat keys such as F, Bb and Eb. As well as this, certain styles (particularly Jazz and Fusion) contain many key changes in themselves. For these reasons, you need to learn how keys relate to each other so you can move quickly between them.
One way to do this is to use the key cycle (also called the cycle of 5ths or cycle of 4ths). It contains the names of all the keys.
To help memorize the key cycle, think of it like a clock. Just as there are 12 points on a clock, so there are 12 keys. C is at the top and contains no sharps or flats. Moving around clockwise you will find the next key is G, which contains one sharp (F#). The next key is D, which contains two sharps (F#and C#). Progressing further through the sharp keys, each key contains an extra sharp, with the new sharp being the 7th note of the new key, and the others being any which were contained in the previous key. Therefore the key of A would automatically contain F#and C# which were in the key of D, plus G# which is the 7th note of the A major scale. When you get to F#(at 6 o’clock), the new sharp is called E# which is enharmonically the same as F. Remember that enharmonic means two different ways of writing the same note - i.e., F#= Gb. Thus the key of F# contains six sharps, while the key of Gb contains six flats - all of which are exactly the same notes.
If you start at C again at the top of the cycle and go anti-clockwise you will progress through the flat keys. The key of F contains one flat (Bb), which then becomes the name of the next key around the cycle. In flat keys, the new flat is always the 4th degree of the new key. Continuing around the cycle, the key of Bb contains two flats (Bb and Eb) and so on. Practice playing all the notes around the cycle both clockwise and anticlockwise. Once you can do this, play chords starting on each note of the cycle, as shown in the next example.
