The circle of fifths is an invaluable tool that reveals important relationships between pitches and organizes them in a way that’s very useful to understanding diatonic harmony.
Below is a guitar chord key chart the major and minor keys. A chord key chart outlines the diatonic chords, or the chords that naturally occur in a given key. Chord charts are useful when trying to figure out the key of a song.
One of the more challenging obstacles as a beginner guitarist, or if you’re just new to guitar theory, is figuring out how to determine the key of a song. Some songs stick to standard chords within a key, which makes this task much easier. Other songs, however, are not as straight forward.