twelvebar

twelvebar, often written twelve-bar, is a term used to describe a common chord progression in blues and related genres known as the twelve-bar blues. The form consists of 12 measures (bars) that typically cycle through the tonic (I), subdominant (IV), and dominant (V) chords, producing a recognizable harmonic backbone for melodies and improvisation.

Although many keys are used, the standard pattern in a major key is often presented in the following sequence: bars 1–4: I; bars 5–6: IV; bars 7–8: I; bar 9: V; bar 10: IV; bars 11–12: I. In practice, performers frequently play seventh chords (I7, IV7, V7) to evoke blues color. Turnarounds in bars 9–12 provide a transition back to the tonic, and many performances substitute slightly different patterns for variety.

Variations abound: the exact chords and rhythms may be altered, the order of IV and V can shift, bar 9 may use V7 instead of I, and some versions end with a longer turnaround or an 8-bar extension preceding the final bar.

Rhythmically, twelve-bar blues is commonly played in a 4/4 time with a swing or shuffle feel, though straight, tempo-flexible interpretations exist. It serves as a framework for improvisation, call-and-response, and ensemble accompaniment.

Notable uses include traditional blues recordings such as Sweet Home Chicago, which popularized the form, and countless blues, R&B, rock and jazz performances. The twelve-bar structure remains a foundational element in blues pedagogy and repertoire.