The blues scale originated out of a need to bridge the gap between the diatonic 7 note scales and modes of European music and the sounds brought to the United States from Africa.
The origins of the blues go back to the early field cries of the Deep South of the United States.
There was a call and response that was sung as the workers worked the fields.
A little known fact is that through these songs stories were told but also gossip and when the Under Ground Railroad (a network of safe houses used to free the escaped slaves) was running information was transferred singing these early hymns and field songs.
So the Blues scale tries to bridge the gap.
You can use the blues scale to get the blues sound by the arrangement of the notes.
The A Blues Scale notes are:
A, C, D, Eflat, E, G 1, min3, 4, flat 5, 5, flat 7
Here is the Blues Scale in A tablature:
The fingering is simple: Place your 1st finger on the 5th fret Place your 2nd finger on the 6th fret Place your 3rd finger on the 7th fret Place your 4th finger on the 8th fret
Notice the A string has frets 5, 6, 7 in a row.
The flat 5 is a dissonant note but when played as a passing note it gives an edge to the sound.
You can also add the major 3rd or C# in this case.
Eventually you will realize in playing the blues that all notes are fair game and it is how you approach each note or series of notes that will make it work or not.
Remember you are trying to emulate the human voice.
I know whenever I hear B.B. King I hear a dialogue in his playing. Its as if I can hear him having an argument with his Old Lady. Her screaming, him pleading for forgiveness or the other way around.
If you learn the blues scale eventually you will be able to draw from your own emotional experience and create your own blues style.
Andrew Koblick has played and taught guitar for 30 years. His site provides free guitar lessons newsletter, discussion forum and guitar links.
Find out more here about Blues Guitar Lessons.