The Basic Blues
Basic blues consists of 3 chord changes. In the key of C, the chords would be C7, F7, and G7. The chords are derived from the scale. C is the I chord, F is the IV chord, and G is the V chord. Using the familiar 12 bar pattern, the basic blues in C would look like this:
Blues 1
Adding Extensions
By adding some extensions to the basic 7th chords, you can make your rhythm playing sound more interesting. Adding 9th's, 13th's, and sharp 9th's is common in blues and jazz.
Blues 1 (variation)