Song structure or the musical forms of songs in popular music are typically sectional, repeating forms, such as strophic form. Other common forms include thirty-two-bar form, verse-chorus form, and the twelve bar blues. Popular music songs are rarely composed using different music for each stanza of the lyrics (songs composed in this fashion are said to be "through-composed"). This form can be used in any structural difference in melodies. A common format would be as listed: Verse, Pre-Chorus, Chorus, Verse, Pre-Chorus, Chorus, Bridge (Middle Eight), Verse, Chorus.
The foundation of popular music is the "verse" and "chorus". Both are essential elements with the verse usually played first. Exceptions abound with "She Loves You" by The Beatles being an early example in the rock music genre. Each verse usually employs the same melody (possibly with some slight modifications), while the lyrics usually change for each verse. The chorus (or "refrain") usually consists of a melodic and lyrical phrase which is repeated. Pop songs may have an introduction and coda ("tag"), but these elements are not essential to the identity of most songs. Pop songs often connect the verse and chorus via a bridge, which as its name suggests, is a section which connects the verse and chorus at one or more points in the song.
The verse and chorus are usually repeated throughout a song though the bridge, intro, and coda (also called an "outro") are usually only used once. Some pop songs may have a solo section, particularly in rock or blues influenced pop. During the solo section one or more instruments play a melodic line which may be the melody used by the singer, or, in blues or jazz influenced pop, the solo may be improvised based on the chord progression.
The introduction is a unique section that comes at the beginning of the piece. Generally speaking an introduction will contain just music and no words. It usually builds up suspense for the listener so when the downbeat drops in, it creates a release or surprise. In some songs, the intro is one or more bars of the tonic chord (the "home" key of the song). The introduction may also be based around the chords used in the verse, chorus, or bridge, or a stock "turnaround" progression may be played, such as the I /vi / ii/ V progression (particularly in jazz influenced pop songs). In some cases, an introduction contains only drums or percussion parts which set the rhythm and "groove" for the song. Alternately the introduction may consist of a solo sung by the lead singer (or a group of backup singers), or played by an instrumentalist.
In popular music a verse roughly corresponds with a poetic stanza. When two or more sections of the song have basically identical music and different lyrics, each section is considered one verse. It is not to be confused with a pre-verse, which is an interlude between the introduction of a song and its opening verse. Although less common now, the pre-verse technique was popular with the surf music of the 1960s.
The element of the song that repeats at least once both musically and lyrically. It is almost always of greater musical and emotional intensity than the verse. In terms of narrative, the chorus conveys the main message or theme of the song. Normally the most memorable element of the song for listeners, the chorus usually contains the hook. In popular music, the chorus normally follows the verse, but there are notable exceptions including The Beatles' "Can't Buy Me Love", The Black Eyed Peas' "Imma Be", Pink's "Get the Party Started" and Linkin Park's "Crawling."
"Many popular songs, particularly from early in this century, are in a verse and a chorus (refrain) form. Most popular songs from the middle of the century consist only of a chorus."
In music theory, middle 8 (or bridge) refers to the section of a song which has a significantly different melody from the rest of the song, usually after the second chorus in a song. (Typically, a song consists of first verse, pre-chorus, chorus, second verse, pre-chorus, 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. Jazz players also call this "the release".
A typical song structure employing a middle 8 is:
.... .... .... .... ........ .... ....
Middle 8s are often quieter than the main song, in contrast with the Solo, which is 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 then end the song with a hook in the end chorus and finale.
A collision is a section of music where different parts overlap one another, usually for a short period. It is mostly used in fast-paced music, and it is designed to create tension and drama. For example, during a chorus later in the song, the composer may interject musical elements from the bridge.
A solo is a section designed to showcase an instrumentalist (e.g. a guitarist or a harmonica player) or less commonly, more than one instrumentalist (e.g., a trumpeter and a sax player). The solo section may take place over the chords from the verse, chorus, or bridge, or over a standard solo backing progression, such as the 12-bar blues progression. In some pop songs, the solo performer plays the same melodies that were performed by the lead singer, often with flourishes and embellishments, such as riffs, scale runs, and arpeggios. In blues- or jazz-influenced pop songs, the solo performers may improvise a solo.
Latin: Ad Libitum, "at will". An ad lib section of a song (usually in the coda or outro) occurs when the main lead vocal or a second lead vocal breaks away from the already established lyric and/or melody to add melodic interest and intensity to the end of the song. Often, the ad lib repeats the previously sung line using variations on phrasing, melodic shape, and/or lyric, but the vocalist may also use entirely new lyrics or a lyric from an earlier section of the song. During an ad lib section, the rhythm may become freer (with the rhythm section following the vocalist), or the rhythm section may stop entirely, giving the vocalist the freedom to use whichever tempo he or she wishes. During live performances, singers sometimes include ad libs not originally in the song, such as making a reference to the town of the audience or customizing the lyrics to the current events of the era. It is important to note the distinction between ad lib as a song section and ad lib as a general term. Ad lib as a general term can be applied to any free interpretation of the musical material.
Thirty-two-bar form uses four sections, most often eight measures long each (4×8=32), two verses or A sections, a contrasting B section (the bridge or "middle-eight") and a return of the verse in one last A section (AABA)..
Variation on the basic structure:
Verse-chorus form or ABA form may be combined with AABA form, in compound AABA forms. Variations such as a1 and a2 can also be used.