Before we jump into scales let's talk about those black keys. As you know, the interval between any black key and the adjacent white is 1/2 step. The black key has the name of the adjacent white key along with its direction. Going up from a C its called a C# (C sharp). That same key going down from a D is a Db (D flat). So the black key actually has two names, depending upon how it is used. The term for this is enharmonic equivalents.
Scale Structure
Now lets get back to the C Major scale. Since we are not using any black keys the C Major scale has no sharps or flats. Every scale has a structure comprised of the collection of notes and the intervals between them. The structure of any Major scale in steps is:
1 - 1 - 1/2 - 1 - 1 - 1 - 1/2
It might be easier to remember this as 2 1/2, 3 1/2.
Were we to begin on G, using this same structure we would have to use an F# as the 7th note because that would be a whole step up from E and 1/2 to the G of the next octave. So the key of G has 1 sharp. But we will get into this more when we look at the Circle of Fifths.
Minor Scales
Every major scale has a relative minor scale. Conversely, every minor scale has a relative major. What does this mean? It means they share the same key signature. Or, more plainly, they use the same notes.
The relative minor of the C Major scale is A minor. If you begin on A and go up using only the white keys (no sharps or flats) those seven notes are the ones in the key of A minor.
Just like the major scale the minor scale has a structure and its intervals are:
1 - 1/2 -1 - 1 - 1/2 - 1 - 1
Again, this might be easier to remember as 1 1/2, 2 1/2, 2. Using this structure and starting on any note will yield its minor scale.
Now let's see how we can use this information to build chords.
