The thirty-two-bar form, often called AABA from the musical form or order in which its melodies occur, also ballad form, is common in Tin Pan Alley songs and later popular music including rock, pop and jazz. Though it resembles the ternary form of the operatic da capo aria its popularity declined and "there were few instances of it in any type of popular music until the late teens" of the 20th century. It became "the principal form" of American popular song around 1925–1926, Examples include "Deck the Halls". with AABA form consisting of the chorus or the entirety of many songs in the early 20th century.
Some Tin Pan Alley songs composed as numbers for musicals precede the main tune with a "sectional verse" that is usually sixteen bars long. The verse establishes the background and mood of the number, and is musically undistinguished in order to highlight the attractions of the main tune. The main tune is called the refrain or chorus. The sectional verse is often omitted from modern performances, and thus the refrain is often the only section remembered and heard.
In the refrain, the A section or verse forms the main melody and is harmonically closed with a cadence on the "home" or tonic chord. The B section or middle eight is also often referred to as the bridge and sometimes as the release. In it a simple modulation is commonly found and at its end it remains harmonically open, often ending on the unresolved dominant chord of the home key and so preparing for the return of the verse.
"In this form, the musical structure of each chorus is made up of four eight-bar sections, in an AABA pattern... Thousands of Tin Pan Alley tunes share this scheme and Adorno is quite justified in arguing that to listeners of the time it would be totally predictable."
Thirty-two-bar form was often used in rock in the 1950s and '60s, after which verse-chorus form became more prevalent. Examples include:
- George Gershwin "I Got Rhythm"
- Jerry Lee Lewis' "Great Balls of Fire" (1957)
- The Everly Brothers' "All I Have to Do Is Dream" (1958)
- The Shirelles' "Will You Love Me Tomorrow" (1960)
- The Beach Boys' "Surfer Girl" (1963)
Though more prevalent in the first half of the 20th century, many contemporary songs show similarity to the form, such as "Memory", from Cats, which features expanded form through the B and A sections repeated in new keys. Songwriters such as the Brill Building and Lennon-McCartney also used modified or extended thirty-two-bar forms, often modifying the number of measures in individual or all sections. The Beatles ("From Me to You" (1963) and "I Want to Hold Your Hand" (1963)), like many others, would extend the form with an instrumental section, second bridge, break or reprise of the introduction, etc., and another return to the main theme. Introductions and codas also extended the form. In "Down Mexico Way" "the A sections … are doubled in length, to sixteen bars—but this affects the overall scheme only marginally". Compound AABA form found in The Police's "Every Breath You Take" (1983), features a thirty-two-bar section, a contrasting bridge and then a repeat of the thirty-two-bar section, making a compound of ABA and AABA form: AABACAABA: a form of rondo. Other examples include:
- Boston's "More Than a Feeling" (1976)
- Righteous Brothers' "You've Lost That Lovin' Feelin'" (1964)
- Led Zeppelin's "Whole Lotta Love" (1969)
- The Rolling Stones's "Brown Sugar" (1971)
- Tom Petty's "Refugee" (1979)
Middle eight 
In music theory, middle 8 or bridge refers to the B section of a thirty-two-bar form. It is often a passage from the tonic into the dominant, often subdominant, or a major or minor key (see modulation (music)).
This section has a significantly different melody from the rest of the song and usually occurs after the second chorus in a song (typically, a song in thirty-two-bar form consists of first verse, chorus, second verse, chorus, middle eight, chorus). Such sections often consist of new chords, but also frequently just alternate between two chords. It is called a middle 8 because it happens in the middle of the song and the length is generally 8 bars.
Middle 8s are often quieter than the main song, which contrasts with solos, which are generally more energetic. In slower songs, however, a middle 8 can be used to generate energy. By adding a powerful upbeat middle 8, musicians can add a great hook for an end chorus and finale.
- Jazz: College Edition: Chapter 2: Jazz Form and improvisation | Jazz: W. W. Norton StudySpace
- Boyd, Jack (1991). Encore!: A Guide to Enjoying Music, p.31. ISBN 978-0-87484-862-5. "It is sometimes called ballad form because so many of our popular ballads, middle-of-the-road popular songs, and Country Western songs use this form."
- Wilder, Alec (1972), American Popular Song: the Great Innovators 1900–1950, New York: Oxford University Press, p. 56, ISBN 0-19-501445-6.
- Benward & Saker (2003). Music: In Theory and Practice, Vol. I, p.317-18. Seventh Edition. ISBN 978-0-07-294262-0. "The popular chorus form is often referred to as a quaternary form, because it usually consists of four phrases."
- Benward & Saker (2003), p.318.
- Covach, John (2005), "Form in Rock Music: A Primer", Engaging Music: Essays in Music Analysis, New York: Oxford University Press, p. 69, ISBN 0-19-517010-5 Unknown parameter
- Middleton, Richard (1990), Studying Popular Music, Philadelphia: Open University Press, p. 46, ISBN 0-335-15275-9.
- Covach (2005), p. 70 Missing or empty
- Benward & Saker (2003), p.122 & 318.
- Covach (2005), pp. 74–75 Missing or empty
- Parkinson, Alice (2006). Music, p.125. ISBN 978-81-89093-50-1.
- Powell, Neil (2000). The Language of Jazz, p.120. ISBN 978-1-57958-277-7.
Further reading 
- Appen, Ralf von / Frei-Hauenschild, Markus AABA, Refrain, Chorus, Bridge, Prechorus — Songformen und ihre historische Entwicklung. In: Black Box Pop - Analysen populärer Musik. Ed. by Dietrich Helms and Thomas Phleps. Bielefeld: Transcript 2012, pp. 57-124. ISBN 978-3-8376-1878-5.