Composing Music and the Circle of Fifths
Part of the Music Composition For Dummies Cheat Sheet
If you're into music composition, you need to know the Circle of Fifths because it shows the relationships between major keys and their relative minors. In the following image, the major keys are indicated with capital letters, and their relative minors are in lowercase. Also shown are the number of sharps or flats that you put in the key signature for each key.