Think you know the blues? Guess again. One of the most important musical forms to the improvising musician, this musical forms lends itself to all sorts of emotions: happy, sad, discontent, anger, or plain old solemn. The branches of the blues can be heard in all forms of music: Rock and Roll, Rhythm and Blues, Delta Blues, Jazz, Texas Swing, Country, Bluegrass. Its all there. The blues is a twelve measure structure containing a particular sequence of chords. The structure may be as simple as the "I-IV-V" chords used by most rock or traditional blues players, to the most complex used by the jazz greats of the be-bop era. Check out the example of a simple blues form. Just a note, no matter the complexity of the chords the standard progressions is still there.