structure of a pop song: definitions
So far we have quickly examined how melody and harmony contribute to create some sort of order and coherency to a musical piece, which otherwise would not sound harmonious and pleasant, but rather discordant and undirected.
However, another element that plays an important role in how music is put together is the structure of the musical piece. We are used to listen to musical piece whose structure we can somehow recognise as familiar and known, especially in popular music. This does not mean that other kinds of music do not have rules or guidelines of this kind: classical music for example is based on models such sonata, fuga, interlude, etc. By choosing what kind of piece to write, a composer is expected to follow specific rules that make that piece recognisable as of a particular kind.
Pop music structure is rather simple compared to classical canons. Being able to recognise music elements is important to a sound engineer because they are used very often in the studio: if a talent asks you to re-record 'from the end of the second verse until just before the bridge' we must be able to understand what he is saying. We engineers are probably more familiar with time codes and absolute time references, but of course it is easier for a talent in the live room to refer to 'the end of the first chorus' rather than to a time like '01:02:35:22', as we would do...
So, that's why we must be able to talk the talk. Here are some definitions of the most common elements of a pop song, and they will be demonstrated in a few examples for a better understanding. Please, understand that there is some degree of generalisation in these definitions, of course there are exceptions:
Stands for introduction, and as you may have expected it is the very beginning of a song. Generally instrumental, it usually finishes with the beginning of the first verse, but sometimes we can find a chorus right after the intro. Usually it contains melodic elements that resemble the chorus or the riff.
A catchy instrumental sequence that very often becomes the most characteristic part of a the song. Usually four to eight bars long. Riffs are used most frequently in rock music. To name a few classics, good examples are the guitar lines in Deep Purple's 'Smoke on the water' or in Rolling Stones 'satisfaction'. A very famous bass riff is Queen's 'Another one bites the dust'. Riffs are usually repeated consistently through the song.
The verse is usually the first lyrical element of a song, therefore it is common that the instrumental parts here tend to work for the vocals, which is mostly highlighted. For the same reason, often verses are calmer and tend to contain less instruments. Verses commonly have a structure based on four lines or multiples of four: this structure is repeated several times through the song, but with different lyrics. It is not rare to find two or more verses in sequence, or perhaps divided by a four or eight bars instrumental part, to enhance the separation.
Not so commonly used but still important, builds are used before a part of the song that is considered important or very characteristic, such a chorus or a solo. A build precedes these parts with the purpose to create an ascending climax sense, which culminates in the part that immediately follows. We can find, for example, a progressively increasing intention with which the band plays, or a slight increase in volume, due to the higher emphasis progressively employed in playing this part. If it contains lyrics, their meaning may lead to a conclusion in the following part and singers may further stress the ascending climax pattern with their singing style. For these reasons, builds cannot be very long, otherwise the climax would not be as effective. They could range from two to eight bars, longer ones are less common.
Choruses play a most important rule in pop music, being the part that is intended to be remembered more easily, since contains the whole identity of a song. Many pop songs are actually written around a chorus. Usually the first chorus starts after a couple of verses, but it is not unusual to hear songs that actually start with the chorus. Think about The Beatles 'She loves me' for example. Many modern pop song feature the chorus within the first minute, or even less. This trend has developed to make sure that the listener is presented with the catchiest part of the song as soon as possible. Choruses are repeated several times during a song, and unlike the verses, the lyrics usually remain the same, or change very slightly. Sometimes, especially towards the end of the song, choruses are transposed to a higher key to further enhance them, or repeated twice or more ('ad libitum') to stress that the song has come to an end.
Pop song employ a very repetitive structure, so it is common to introduce some elements of variation. Bridges, or specials, are usually put after a second or third chorus, so in a later stage of the song, and they may contain melodic and harmonic variations to the song. Often they are transposed to a higher key, which can be kept until the end of the song or restored to the original after the part, and they tend to convey some sort of unexpected elements that surprise the listener: a new instrument, or a different vocal melody, or different dynamics. After the special the song usually arrives soon to an end.
A solo is an instrumental part where a particular instrument is dominant. It usually features virtuoso parts that show the musical skills of the player. Guitar solos are very common in rock music, but also keyboard/synth solos are very popular. Depending on the genre, different instruments are used more frequently: in jazz music brass instruments are widely used for example. Even instruments that are usually dedicated to the rhythm parts can perform a solo: bass and drums solos are common and very effective. More rarely, it is possible to find vocal solos as well. Commonly (but not always) the melodic elements of the chorus are employed in a solo.
A breakdown, like a special, is usually employed to include some variation in the otherwise repetitive structure of a pop song. In a breakdown, there is a sudden change of the dynamic of the song, and most instruments stop playing apart from a few. Commonly only the drums are left, or only a rhythmic guitar. Sometimes breakdowns contains lyrical parts, in which case the voice could unaccompanied by instruments or it can be supported by a drum patter or a simple riff, or both. Breakdowns are usually four bars or eight bars long, and they often lead to a chorus or a solo, to achieve an effect similar to the builds.
The last part of the song. It is often instrumental and it can be a part specifically designed to be a coda, or also a repetition of a previously used parts (most commonly the riff or the chorus) that fades out into silence. A solo can also be used as a coda. Some songs do not have a coda at all, they just finish abruptly after a chorus or after an ending verse.
The definitions are not in a particular order, but songs tend to follow some kind of common pattern with regard to their structure.