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music_manuscript “AAB” Song Form, also called 12 Bar Blues Song Form is one of the main traditional song forms. Both names are regularly used by songwriters to describe this song form.

This article explains the fundamentals of AAB Song Form, and provides examples of AAB Song Form being used in popular rock and blues songs.

If you are uncertain of the meaning of some terms, please visit our music glossary.

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This article is focused on providing a basic understanding of AAB Song Form in the modern era, so some root musical forms or classifications of musical forms have been referenced for completeness.


Song Building Blocks

Popular music, in particular, often uses a number of common structural song parts.

The common building blocks are:


  2. VERSE
  10. CODA / OUTRO

For details about these song building blocks please read our article, "Song Building Blocks".


AAB Song Form - 12 Bar Blues Song Form

The 12 bar structure used in the AAB pattern is a very common structure in blues music. Many Blues songs are structured using the AAB format. Unlike AAA or AABA song forms, which describe the overall structure of the song, AAB describes the structure of an individual verse. AAB is always used as a compound form

12 bar relates to the number of bars, or measures, in this song form. Almost all Blues music is written in a 4/4 time signature, i.e. there are four beats in every measure or bar with each quarter note (crotchet) being equal to one beat.

There are a lot of rock and other blues derived songs that use 12 bar song form, it's derivatives, or a hybrid or compound form involving AAB.


Structure Of AAB Song Form

AAB / 12 Bar Blues is the most common blues song form. An AAB pattern is used in both lyrics and melody (this is often set out in a "question-question-answer" format) made up of three 4 bar phrases in AAB Song Form.

The fundamental structure of 12 Bar Blues is three four-bar lines or sections. Often the first two and a half bars of each 4 bar section are vocal melody, while the last one and a half bars contains an instrumental melodic hook that gives a sense of completion for the line. The instrumental melody often answers, echoes, repeats, or compliments the vocal melody being sung in the first two and a half bars.



The AAB A Section

In 12 bar blues, the first and second lines (the two A sections) are often a identical in terms of both the lyrics and the melody. Often the A sections forms a question or makes a statement.


The Refrain - The AAB B Section

AAB form doesn't have a chorus section. The last line or third 4-bar section is the refrain. The major hook of the song often makes use of the song title. The main hook is commonly a part of the refrain. The refrain often forms a response or answer to the question, or a comment on any statements, made in the previous A sections. The refrain ends with a cadence or half cadence. When leading to another verse one of many standard "turnaround" transitions are used.


Example AAB Song Form using a 12-Bar Blues Chord Progression

A standard Blues chord progression, in AAB Song Form, uses (but is not limited to) three chords. These chords are based on the first (I), fourth (IV), and fifth (V) notes of the eight-note scale.

  1. The I chord dominates the first "A" section
  2. The IV chord typically shows up in the second "A" section
  3. The V chord typically appears in the "B" section



In the example above, the I chord is played over the first, third and fourth bars and the IV chord is played over the second bar, but it isn't uncommon for this first A section to only use the I chord.

The second A section uses the same chord progression, the only difference being that the first I chord is replaced with one bar of the IV chord. The lyrics and melody of each A section often act as a question.

The B section, or refrain, begins with the V chord. As an answer to questions posed in the preceding A sections, the B section finally resolves to the I chord (creating a full cadence) or to the V chord (creating a half cadence). Our example uses a half cadence in bars 9-12. A cadence, of any kind, marks the end of the song or section of a song. When it cues another verse or stanza, the transition from one verse or stanza to the next is known as "The Turnaround". There are a number of standard turnarounds that can be used. The example B section may also use a different lyrical meter and melody in when compared to the two preceding A sections.

This chord progression is not the only AAB Song Form chord progression, but it is typical of the AAB Song Form.


Video examples of AAB / 12-bar blues Song Form

  1. "Crossroad Blues" (Robert Johnson, 1936)
  2. "Sweet Home Chicago" (Robert Johnson, 1936)
  3. "Dust My Broom" (Robert Johnson/Elmore James, 1936)
  4. "Pride and Joy" (Stevie Ray Vaughan, 1983)


Not all blues songs follow the 12 bar structure. Some songs use the same essential AAB layout, with the exception that either 8 bars, 16 bars or 24 bars are used.

Example of 16 Bar Blues:

  1. "Hoochie Coochie Man" (Muddy Waters, written by Willie Dixon 1954)

Examples of 24 Bar Blues:

  1. "Mustang Sally" (Wilson Pickett, written by Mack Rice 1965)
  2. "Carol" (Chuck Berry, 1958)

Discuss this article in our Music Forum.


John Moxey

Songstuff Site Crew


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