BLUES FORM The word  “blues” means a music style, a way to perform, a musical form, and a mood. In structure, the main characteristic is a repeated harmonic 12-bar pattern in 4/4 key signature. This 12-bar period is divided into three 4-bar phrases, the first in the tonic, the second in the subdominant and tonic, and the last in the dominant and tonic. The classic harmony  The harmony, although it seems to be a major-mode, is neither major nor minor. Blues sound comes from the simultaneous use of major and minor tonalities. An important characteristic of the blues is the use of notes that are unstable harmonically and functionally.