Do you know what they say about rules? They say lots of things about rules but here are two - rules were made to be broken, and you have to know what the rules are before you can break them. While Judge Dredd may not agree with the first, the second is certainly true and never more so than in writing a song.
The song structure may not be the first thing you think about when you start writing. You probably work on the verse or chorus, or maybe you have a good riff that you want to expand into a song. So you get that down and then you start to think about the other parts - the intro, how many verses, middle eight, do you want an instrumental, the ending...
Some song genres have a fairly rigid format, others are more flexible, and you need to know where you can bend the rules and why you may not want to do so to make your song stand out from the others. Let's look at the sections you'll find in most songs and the part they play in song construction.
Intro. Yes, this leads you into the song. It may be two, four, or eight bars long or longer. Some songs don't have an intro at all. A pop song intro will often be reminiscent of the chorus or the hook. In a club song, it's often a good idea to have eight bars of rhythm to help the DJ mix match your song. They say that music publishers typically only listen to the first 20 seconds of a song before deciding whether to reject it so if you're sending material to a publisher, keep the intro short and get into the song as quickly as possible. Save the 5-minute intros for the CD version.
Verse. This is the preamble to the chorus. It sets the scene, certainly lyrically, and as the verses progress they often tell a story or recount episodes from a situation although that's by no means essential. They are typically eight or sixteen bars long and melodically not usually as strong as the chorus although, again, that's by no means essential. However, it often seems as if the songwriter ran out of ideas when writing the verse. One of the strengths of The Beatles' songs is that verses and choruses are equally strong and most people could hum or sing their way through most Beatles hits. Not so with many songs where the verses are little more than fillers to get you to the chorus.
Chorus. This the bit everyone remembers, whistles, and sings along to. It should be the strongest part of the song and generally is or contains the hook. It's usually eight or sixteen bars long.
Middle eight. As a song progresses, there's a danger of boredom setting for the listener. The middle eight offers them a break and typically comes after a couple of verses and choruses. Some people think of it as an alternative verse and that's one way to look at it. It often modulates to a different key or introduces a new chord progression and it usually doesn't include the song title. However, all too often it's simply an excuse for waffling on for a few bars. Although it's called the middle eight it could be four or sixteen bars long.
Bridge. Many people use the terms 'middle eight' and 'bridge' synonymously and so popular is this usage that it would be churlish to disagree. However, among those who prefer to note the difference, a bridge is a short section used to bridge the gap between verse and chorus. It may only be two or four bars long and it's often used when the verse and chorus are so different from each other that a 'joining' phrase helps bring them together.
Instrumental. This is part of the song without any vocals. Yeah, okay. It's often an instrumental version of the verse or chorus, it may be an improvised variation on one of these, or it may be an entirely different tune and set of chords altogether. Sometimes it fits into a song where a vocal middle eight would otherwise go.
Breakdown/Break. This term has been high jacked from songs from the early 1900s when it was common to either reduce the instrumentation or stop it altogether while a tap dancer would strut his stuff. The term 'break' is still sometimes used to indicate an instrumental section. 'Breakdown' is now most commonly used in dance music for the section where the percussion breaks down or is reduced, and it may be the dance equivalent of the middle eight.
Outro/Ending. Once upon a time, songs had definite endings but the mid-1950s heralded in the era of the fade-out and songwriters thought they would never have to write an ending again. However, fade-outs became such cliches to the extent that fade-out meant cop-out so songwriters started writing endings again. With that in mind, you can do as you wish, and considering that the endings of most songs get talked over or cut short by radio DJs and mixed over by club DJs, you have only your artistic integrity and your CD listeners to answer to. Some songs work extremely well with fade-outs but listen to songs in your chosen genre to see how other writers approach endings. But whatever you do, avoid like the plague the three-time tag ending.
Hook. The hook is not a song part as such; rather it's the term used to describe the part of the song that people remember and sing. It's what they buy the record for. It's usually the chorus although it need not be the entire chorus, but simply a two- or four-bar phrase. It could be an instrumental riff as in Whiter Shade of Pale or Smoke on the Water, or a processed vocal as in Cher's Believe.
All Together Now
Having described the parts of a song, let's see how they are commonly arranged. The most popular arrangement by far is simply verse-chorus and repeat. Here are two variations on the theme:
Intro Verse 1 Chorus Verse 2 Chorus Chorus Outro
Intro Verse 1 Verse 2 Chorus Verse 3 Middle eight Chorus Chorus Outro
You get the picture. However, these are conventions rather than rules so you can adapt, change or ignore them as you see fit. But they have developed for a reason and that is simply to make the song as immediately appealing to the listener as possible.
Listen to some of the Stock, Aitken, and Waterman hits of the 80s (it's not compulsory if you really can't bear to) and you'll see that most follow the simplest format, guaranteed to brainwash the listener with as many repeats of the hook as possible. They tend to be:
Intro (similar to the chorus) Verse 1 Chorus Verse 2 Middle eight Chorus Chorus Outro
Notice that the hook's there straight away in the intro, there's only one verse before the chorus so you get to it quicker, and the chorus tends to repeat at the end, just to imprint the hook firmly in your mind.
There are obvious exceptions to these formats. Ambient, trance, chill-out music, and the like, are obvious candidates. With these, you can start at the beginning and work through to the end creating an evolving music form without any clear verse/chorus structure. Genres such as trance tend to build to a series of crescendos several times throughout the song. However, even these types of songs often have a hook or two on which listeners can hang their hat.
Build Ups And Downs
Bearing in mind that the purpose of a song is to keep the listeners listening and not allow them to get bored, you need variety within the song. Simply strumming a guitar and singing verse/chorus/verse/chorus won't cut the mustard unless you're in a folk club. The usual method is to start with a simple arrangement and add to it as the song progresses.
So, the first verse might consist of light drums, bass, and rhythm guitar. As you move into the second verse you could add strings or a synth pad. A drum fill takes you into the chorus which would include busier drums, maybe some additional percussion, a fuller string arrangement, and perhaps a lead line. When you dip back to the verse, you revert to the simpler arrangement.
The middle eight is usually a lighter arrangement than the chorus and allows you to use different instrumentation if you want to. When you hit the second chorus, add backing vocals and a lead riff. The final chorus is the culmination of the song and you can add more backing vocals, more percussion, and additional lead lines.
Listen to songs in the style you are writing and analyze their formats to see how far other exponents have stuck to or departed from the traditional formats. when you're familiar with the rules or conventions that they use, then you can experiment by breaking them.