Description
Now that we know the First Law of the Blues, known as 12 Bar Blues Form, we need to pick a key to use in order to use the 12 Bar Blues Form. We'll use A major for this tutorial.
In the key of A major we have the follow notes:
We take the 1st, 4th and 5th notes - A, D and E - and build chords upon them. This results in the three chords we will use for our 12 Bar Blues Form.
We can get and will get into more detail concerning the theory of using Roman Numerals later on. For now, keep this in mind, we use Roman Numerals (I, IV, V) for identifying the chords in a chord progression. In order to build the stereotypical 12 Bar Blues Form in A major we use the I, IV, V chords in a very specific order.