The standard 12-Bar Blues has three chords:

I

IV

V

As we covered earlier, these chords are based on the notes of the major scale.

The Roman numeral refers to root note of the chord. For the I chord the root note is the first note in the scale.

The first note of the C major scale is a C.

Chords are made of the first, third, and fifth note played together.

A I chord for C would include a C, E, and G notes.

In the key of C

I = C E G

IV = F A C

What would be the V chord?

Playing the chords on a piano

In order to play these chords on a piano, you need to find them on the keyboard. Use this diagram to find the notes for the three chords.