There's not a great deal of theory connected with blues guitar but there certainly is a lot of discussion and a great deal of misunderstanding. Let's start with taking a look at blues in the key of E. Some guitarists assume that the basic scale for playing blues music in this key would be the E minor pentatonic with flattened fifth. Your chords would be E, A and B or I IV and V. The fact is that most blues guitar players use a mixture of scales when they play solos.

The Mixolydian scale is similar to the major scale but unlike the major scale, it has a flattened seventh. The thing to remember with the Mixolydian is that the root note is the fifth note of the key you are playing in. So if you are playing in the key of E the Mixolydian scale starts at B.

You can get some understanding of how to use the Mixolydian scale in blues improvisation by playing the major scale a perfect fifth below the chord you are playing. So to use the Mixolydian over an A chord you play the D major scale, but beginning with the note A.

It's really better to approach the blues through playing rather than theorizing. Once you are able to play basic twelve bar blues using the minor pentatonic scale, you should learn some turnarounds. The turnaround is the bit at the end of the twelve bars that sets you up for the next verse. Start by trying to imitate what you hear on records. Even if you think your solos don't sound very good, you will be amazed at how much better they sound once you have mastered a few turnarounds.

Another thing you need to learn the blues is to listen. Not just in the way we usually listen to music, but as a part of your guitar practice. Half an hour or so of listening to the great blues guitarists will soon make itself felt in your playing.

When you are learning the art of improvisation you can play single notes on a guitar or you can play chords. For a solo guitar player there's a choice between playing an improvised solo over a chord progression or you can play single note melody accompanied by base notes on open bass strings.

Playing a single note tune accompanied by bass notes on one or two open strings helps train your ear and, with regular practice, gives you the knack of letting the notes follow each other under your guidance. The intensity of performing with other musicians in front of an audience often kills the most valuable quality an improvising guitarist can develop - the ability to listen to and respond to the music that the singer, bass player, drummer and rhythm guitarist are making.