Before we dive into the diatonic chords of the minor scale, let me answer a common question students have at this stage: What determines if a song is in a major key or a minor key? If all the chords are the same between relative major and minor keys, what makes a major key different from a minor key?
The answer is where the harmonic “center” of the music is. Or, in other words, where the music resolves, or comes to rest.
The Harmonic “Center”
A song in a major key will revolve around the chords and notes of the major scale and will come to rest on the tonic (I) of the major key. A song in a minor key will, similarly, revolve around the chords and notes of the minor key and come to rest on the tonic (i) of the minor key.
Where Does It End?
Since we determine the key by its point of rest, you can best determine a piece of music's key by where it ends (or wants to end).
Many students wrongly assume a song will always begin on the first note or chord of the key. Many songs do indeed start there, but not always. For instance, the famous riff from the song Oh, Pretty Woman by Roy Orbison outlines an E9 chord riff which is the V chord in the key of A major. Oh, Pretty Woman, however, ends on A and is considered to be in the key of A.
Another example is the song Can't Buy Me Love by The Beatles. It starts on an Em chord, but ends on C. Em is the iii chord in the key of C.
Introductions in songs are meant to drive you forward into the heart of the song, so it makes sense not to start a song on a point of rest. You can't reliably determine a song's key by where a song starts.
What's more reliable is to go by where a song ends. Songs are much more likely to end on the first note or chord of the key. And, that makes sense because the end is where you want everything to come to a stop.
So, if a song is using chords all from C major/A minor and it ends on a C chord, it's in the key of C major. If, instead, it ends on an Am chord, it's in the key of A minor.
You can also look to the melody of a song and notice where it ends. Melodies typically resolve to the tonic note of the key.
Again, if a song's melody notes all fit within C major/A minor and the final melody note is C, it's in C major. If it ends on A, it's in A minor. Usually the final chord and note will resolve to the same major or minor tonic.
Listen to the following recorded examples:
It Could Be Both
Occasionally a song will have parts which strongly suggest the major key and other parts suggest the minor key. For example, it's quite common for songs to have verses which revolve around the minor key and choruses around the major key, or vice versa. Bob Marley's song Could You Be Loved is a perfect example. You can think of this scenario as a key change between the relative major and minor.
In another case, perhaps a song's melody doesn't come to rest on the major or minor tonic note and the final chord does not suggest a key either. In these rare cases where it's ambiguous, remember it won't matter if you call it major or minor as long as everyone is playing the correct chords and notes. You could even say something like, "It's in the key of C/A minor." Musicians would understand you.
It Could Be Neither or More Complicated
Finally, a piece of music might not be in either a major key or minor key. Even though the major/minor key system accounts for a lot of music, there are other systems of harmony which we haven't yet discussed which are not these major or minor key structures.
Because all we've covered so far is major/minor, you might be tempted to force everything into this binary major/minor key system. But, there are more than just those two possibilities. First, however, it is essential to understand the major and minor key system well because it will help you understand these other harmonic systems we will examine later.
Don't worry...all of these different harmonic systems will eventually make sense. The fog will keep lifting if you keep studying! It's not difficult; you just need to keep at it.
Remember: Listen for where the harmonic center is. It's like musical gravity. Where does the music want to come to a stop? It won't be long before these sounds and ideas become intuitive for you.
Check this lesson's songs page for examples of the ideas in this lesson. You don't need to play them necessarily; just read and listen.
Are you ready to begin the diatonic chords of the minor scale?