The blues scale is one of the most important scales in jazz.
“The blues is the key to all things American (except classical music).” – Branford Marsalis
It is the tonal base for the improvisation on the so-called blues scheme.
The structure of the Blues Scale is:
The standard blues scheme is the 12 bar blues form:
The special feature of this “classical” blues scheme is that it uses only dominant seventh chords (the chord of the 5th degree of a major scale).
This blues scheme has been expanded over the course of time and especially modified in jazz.