This tutorial was inspired by an e-mail that I received from M. Hodgson of Manchester (sorry to sound formal, M, but you didn't include your first in your message).
There are a few tutorials here already which cover the subject of which notes occur in which keys. In particlar, there are a couple introducing the major and natural minor scales.
Something that becomes apparent is that the same combinations of notes can occur in more than one scale or key. For example, the same notes occur in both the C major scale and the A natural minor. However, a piece of music written in C major will sound different to a piece written in the relative natural minor key. The question is how to tell which is which?
This tutorial touches on some theory which is covered in a number of other tutorials on the site. If you find that you don't understand any of the concepts discussed, then check the tutorials index as there should be something which covers it. If you do get stuck, then feel free to get in touch with me.
First off, it's worth reminding ourselves that major and minor keys have fairly distinctive sounds. Compare the sound of a major chord with that of a minor chord, or play through a major scale followed by a natural minor scale. You should notice that the major has a 'happier' sound compared to the more sombre-sounding minor. The same is true of the two keys. If a piece of music has a generally 'happy' kind of sound then chances are it's in a major key; if it's a sad sounding ballad then the clever money is on it being in a minor key.
That kind of answers the basic question of 'major or minor?' but it's worthwhile understanding why. That's where the theory side of things comes into play.
We know from previous tutorials that a major key and its relative natural minor contain the same notes and, therefore, the same chords. Let's consider the keys of C major and A natural minor as examples:
| C Major - C D E F G A B | A Natural Minor - A B C D E F G | |||||||||||||||||||||||||||||||||||||||||||
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With me so far? OK, now lets consider a common chord progression in a major key:
Two things to notice here. Firstly, consider not just the chord names, but how they relate back to the parent key. Secondly, notice how the progression starts and ends on a C major chord - the tonic chord. It's also worth pointing out that the closing chord change is from the V chord to the I chord - a perfect cadence. This motion is strongly indicative of the key, moving from the dominant to the tonic sound.
Now, by rights that same chord sequence could be seen as just being chords from the key of A natural minor, but when we think of it in terms of chords from the parent key we can see that the progression would be more like this:
That's the basic progression in triads. Now let's look at the same basic progression, but using 7th chords rather than simple triads.
If you're observant then you'll notice that there's something in that last progression which, strictly speaking, doesn't belong. In place of the diatonic (belonging to the key) chord of Em7 (E-G-B-D) is an 'outside' chord, E7 (E-G#-B-D). The arrangement of notes in that chord gives a much better resolution back to the tonic chord.
Rather than going into this chord substitution in detail here, it's covered it in a separate tutorial about the perfect cadence which includes some information about chord substitution in a minor key.
The very basic rule of thumb is 'happy=major, sad=minor', but as the above shows there is some theory to explain just why the notes come out sounding one way or another. To get to grips with this you need to understand the theory behind scales and chord construction - so take the time to read up on these. There are a number of other tutorials on this site to help you, and like I said earlier, if you get stuck then ask me for help. Good luck!
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