Relative Keys
If you compare the A natural minor minor scale with the C major scale you will notice that they contain the same notes (except starting 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.
Major Scale: C Major
Relative Minor Scale: A Natural Minor
The harmonic and melodic minor scale variations are also relatives of the same major scale, e.g., A harmonic and A melodic minor are relatives of C major. For every major scale (and ever major chord) there is a relative minor scale which is based upon the 6th note of the major scale. This is outlined in the following table.
Both the major and the relative minor share the same key signature, as illustrated in the following examples:
To determine whether a song is in a major key or the relative minor key, look at the last note or chord of the piece. Songs often finish on the root note or the root chord which indicates the key. For example, 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.
Here is a Classical style piece which alternates between the key of D minor and its relative F major. Both these keys share the same key signature which contains one flat (Bb).
The C# note which occurs in this melody comes from the D harmonic minor scale. Some sections of this piece are quite tricky, so play it slowly with a metronome until you can play it perfectly, then speed it up gradually.
