Most guitarists, at some point, want to dig into the blues a bit.  Even if it's not your main genre you can still get a lot of enjoyment out of a good 12-bar jam session.  The blues is a deceptively simple style.  The basic building blocks (5 notes and 3 chords) are simple to grasp, but it can take much longer to really master the style and create your own voice within it.  As a young player, I thought I knew all I needed about the blues... until I started playing with some real blues guys.  I was quickly put in my place and went back to work.

But here we just want to get you started with the basics.  Our two basic elements of the blues are the 12-bar chord progression and the minor pentatonic scale.

A fundamental difference between blue songs and popular music (in any genre) is the form.  In a pop song you've got verses, choruses, and bridges.  A blues tune only has choruses.  The same 12 bars are repeated as many times as you want.  That sets the jam session entry bar a bit lower because you don't have to work out a bunch of transitions and sections with the other players.  Just jump in. 

A standard 12 bar blues looks like this:

| I | I | I | I |

| IV | IV | I | I |

| V | V | I | I |

Or written another way:
4 bars of the I chord
2 bars of the IV chord
2 bars of the I chord
2 bars of the V chord
2 bars of the I chord

So, in they key of A, that would be A for the I chord, D for the IV chord, and E for the V chord.  Usually, all of those will be 7th chords rather than regular triads.

There's also a few common variations you'll see:
- In the 10th bar you can go to the IV chord for one bar instead of hanging on the V.

- In the 12th bar you can go to the V chord instead of hanging on the I.  This is called a Turnaround and sets up a nice tension to transition back to the top of the next chorus.

- In the 2nd bar you can go to the IV chord, returning to the I in bar 3.  This is called a Quick Change and is often used in a slow tempo song to alleviate the boredom of 4 bars of really slow I chord.  It is often used in faster tempo songs as well.

Switching from harmony to melody, your other major blues tool is the minor pentatonic scale.  It has just 5 notes in, as opposed to the normal 7-note western scale, hence the name PENTAtonic.  The origins of the scale are Asian and African, but takes on a totally different character in the blues.

The notes are 1 b3 4 5 b7
In the key of E that would be: E  G  A  B  D

You'll be surprised at how may ideas you can get out of those 5 simple little notes.  The most common guitar fretboard pattern for the minor pentatonic is a "box pattern" rooted from the 6th string:

A minor Pentatonic


This is a movable pattern.  I want you to think less about fret numbers and learn it as a finger pattern on the fretboard.  Then it's simple to move it to any key you need.  If you need the key of Bb start at the 6th fret.  The key of F will start at the 1st fret.

The starred (*) notes are the roots of the key.  In the tab case above, those are the note A. 

Notice also the notice in parenthesis on the third and fifth strings.  These are optional notes that we call "the blue note".  In technical terms it's a b5.  It's one of the notes that makes the blues sound like the blues.  Very emotive, very powerful.  Use is strategically to put an extra twist into your melodies.

Make sure you learn that scale in all 12 keys, which is simple since you're just moving the same pattern to different frets.  Start using it to solo over those 12-bar progressions and you'll be on your way to being a blues cat in no time.

Where do you go from here?  Your next step would be learning a major pentatonic scale and how it relates to the minor pentatonic.  You also might want to start working on targeting specific chord tones in your improvised melodies.  Plenty to learn after that, but these are good starting points.

Lastly, listen to as many blues artists as you can.  Whenever you're learning a new style, listen to as much of it as you can to absorb as much of the language as possible.  The basics here are easy.  To really sound good, there's lots of little details to pick up.  Listen to BB King, Albert Collins, Stevie Ray Vaughan, Robert Johnson, and Buddy Guy for a good blues guitar primer.