Thu Nov 05, 2009 1:33 pm
To expand on my previous post. Starting at C, G is a fifth above C and F is a fourth above C. This works no matter where you start on the circle, the clockwise is the 5th the counterclockwise is the 4th.
However, there is another way to look at it (you really didn't think it was going to be that simple, did you?). This is where dominants and sub-dominants come in. We''ll start with C again, the G is a5th above C (the Tonic) and is called the dominant chord. Going the other direction F is a 5th "below" C and is the sub-dominant.
So, even though F is called the 4th in the key of C counting forward it is also the 5th counting backward. So, the 4th of a key is not called sub-dominant because it is one less than the dominant, it is called sub-dominant because it is a 5th back from the tonic.
Hence, on the circle of fifths any note clockwise from your starting note is the 5th or dominant, any note counterclockwise is the 4th or sub-dominant.
Ric