Relative Keys
If you compare the A natural minor scale with the C major scale you will notice that they contain the same notes; the only difference is that they start on a different note. Because of this, these two scales are referred to as "relatives"; A minor is the relative minor of C major and vice versa.
The harmonic and melodic minor scale variations are also relatives of the same major scale, e.g. the A harmonic and A melodic minor scales are all relatives of C major.
For every major scale (and every major chord) there is a relative minor scale which is based upon the 6th note of the major scale. This is outlined in the table below.
Both the major and the relative minor share the same key signature, as illustrated below.
To determine whether a song is in a major key or the relative minor key, look at the last note or chord of the song. Songs often finish on the root note or the root chord which indicates the key. E.g., if the key signature contained one sharp, and the last chord of the song was Em, the key would probably be E minor, not G major. Minor key signatures are always based on the natural minor scale. The sharpened 6th and 7th degrees from the harmonic and melodic minor scales are not indicated in the key signature. This usually means there are accidentals (temporary sharps, flats or naturals) in melodies created from these scales.
This example keeps alternating between the relative keys of C major and A minor. The arpeggio style of playing used here is particularly effective when playing a Rock ballad.
