what is a key? part ii

If you read part i of this series and found yourself thinking WTF??? have no despair: this post will (hopefully) be a bit more clear and get us nearer to understanding what a key is.

Let's take a common chord progression:

Cmaj | Amin | Dmin | G7 |

Let's examine the notes of all these chords:

Cmaj = C, E, G
Amin = A, C, E
Dmin = D, F, A
G7 = G, B, D, F

If we put all these notes together side by side we get the following:

C, E, G, A, C, E, D, F, A, G, B, D, F

And if we take out the repetitions of a given note we will obtain:

C, E, G, A, D, F, B

Lastly we could put them in ascending order:

C, D, E, F, G, A, B

This group of notes may look familiar: it's the C major scale. (You might have put the notes in order beginning with A, obtaining A, B, C, D, E, F, G, aka A aeolian, aka the A natural minor scale. Same group of notes. Improvisationally it won't matter how you think of it.)

This is a clear example of, or a very clear articulation of a C major scale. But the scale actually is just an abstract way of organizing notes. They aren't actually encountered in the scalar order in this progression. To make a distinction we say that the above progression is in the key of C major. Just keep in mind that a key and scale are really the same thing:

A scale is a way of presenting the notes in a very clear manner.
A key differs from a scale in that the notes can come in varying orders and combinations.

Next post will deal with dominant 7th chords and how they help to determine a key,,,