The
blues scale formula
A scale formula shows how the notes relate to a
major scale with the same root. The major scale is the constant
to which you compare all other scales. The formula for a major
scale is just 1 2 3
4 5 6 7. There are only 7 different notes in a major
scale. The numbers in a scale formula are sometimes referred to
as the scale functions. That just means that each note in a scale
has a certain sound or role in relationship to the root of the
scale. So a D note functions as the 2 in a C major scale.
C D E F G A B C -
C major scale
1 2 3 4 5 6 7 1 - scale functions
Therefore if any note in a particular scale is different than
the major scale with the same root, you will show how it is altered
by a  (sharp)
or a 
(flat) symbol.
So the scale formula for a blues scale is 1
3 4 5
5 7.
In a C blues scale there is an E,
and in a C major scale there is an E.
So you call the E
a 3
since is is a half step lower than the 3rd note in a C major scale.
C E
F G G B
C - C blues scale
1 3 4 5
5 7 1 - scale
functions
Here is the scale formula applied to the basic blues scale form.
Understanding the function of each note helps you to train your
ear to know what a particular note will sound like, before you
play it.
|- 3--|-----|--4--|-5--|
-1st string
|-7--|-----|--1--|-----|
|--4--|-5--|--5--|-----|
|--1--|-----|-----|-3--|
-4th string
|
8th fret
Page 1, Blues scale basics
Page 3, 5 position of an A
blues scale 
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