One variant using this progression is to couple one eight-bar blues melody with a different eight-bar blues bridge to create a blues variant of the standard 32-bar song. "Walking By Myself", "I Want a Little Girl" and "(Romancing) In The Dark" are examples of this form. See also blues ballad.
Eight bar blues progressions have more variations than the more rigidly defined twelve bar format. The move to the IV chord usually happens at bar 3 (as opposed to 5 in twelve bar). However, "the I chord moving to the V chord right away, in the second measure, is a characteristic of the eight-bar blues."
In the following examples each box represents a 'bar' of music (the specific time signature is not relevant). The chord in the box is played for the full bar. If two chords are in the box they are each played for half a bar, etc. The chords are represented as scale degrees in Roman numeral analysis. Roman numerals are used so the musician may understand the progression of the chords regardless of the key it is played in.
Howlin Wolf's version of "Sitting on Top of the World" is actually a 9 bar blues that adds an extra "V" chord at the end of the progression. The song uses movement between major and dominant 7th and major and minor fourth:
The first four bar progression used by Wolf is also used in Nina Simone's 1965 version of Trouble in Mind, but with a more uptempo beat than Sitting on Top of the World:
There are at least a few very successful songs using somewhat unique chord progressions as well. For example, the song Ain't Nobody's business as performed by Freddie King at least, uses a I III IV iv progression in each of the first four bars. The same four bar progression is used by the band Radiohead to make up the bulk of the song 'Creep'.
(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.) For example "Nine Pound Hammer".Ray Charles's original instrumental "Sweet Sixteen Bars" is another example.