An eight bar blues is a typical blues chord progression, taking eight 4/4 bars to the verse. The blues is a vocal and instrumental form of music based on a pentatonic scale and a characteristic twelve-bar chord progression. ... In music and music theory, a chord (from the Middle English cord) short for accord is three or more different notes or pitches sounding simultaneously, or nearly simultaneously, over a period of time. ... The time signature (also known as meter signature) is a notational device used in Western musical notation to specify how many beats are in each bar and which note value (minim (half-note), crotchet (quarter-note), quaver (eight-note), and so on) constitutes one beat. ...

A basic example of the progression would look like this, using T to indicate the tonic, S for the subdominant, and D for the dominant, and representing one chord per beat: The tonic is the first note of a musical scale, and in the tonal method of music composition it is extremely important. ... In music, the subdominant is the technical name for the fourth degree of the scale. ... In music, the dominant is the fifth degree of the scale. ...

 T T S S T T T T S S S S T T T T T T T T S S S S T T D D T T T T 

(The same chord progression can also be called a sixteen-bar blues, if each symbol above is taken to be a half note in 2/2 or 4/4 time -- blues has not traditionally been associated with notation, so its form becomes a bit slippery when written down.) Sixteen-bar blues is a blues chord progression very similar to the eight bar blues form, except that blues is not traditionally associated with any set notation so sometimes it can be called sixteen bars instead of eight. ...

Many variations are possible. For instance, seventh chords are often used just before a change, and more changes can be added. A more complicated example might look like this, where "7" indicates a seventh chord: A seventh chord is a chord or triad which has a note the seventh above the tonic in it. ...

 T T S7 S7 T T T7 T7 S S S7 S7 T T T T T T T7 T7 S S S7 S7 T T D7 D7 T T T D7 

When the last bar contains the dominant, that bar can be called a turnaround. In music, the dominant is the fifth degree of the scale. ...

Finally, here is an example showing the pattern in the key of D, and how it fits with the lyrics of a given verse. One chord symbol is used per beat, with "-" representing the continuation of the previous chord:

 D - Woke up this morning with the G - D - D7 - blues down in my soul G - Woke up this morning with the G7 - D - - - blues down in my soul D - D7 - Woke up this morning with the blues in my soul G - Saying "My baby gone and left me, got a G7 - heart black as coal" D - Woke up this morning with the A A7 D - A7 - blues down in my soul 

Some well known eight bar blues are "Ain't Nobody's Business," "Cherry Red," and "(Romancing) In The Dark."

See also: twelve bar blues, chord progression. Twelve bar blues is a chord progression, typical of blues and later, blues-influenced, music. ... A chord progression (also chord sequence and harmonic progression or sequence), as its name implies, is a series of chords played in an order. ...