It’s a funny word, but it’s critically important.
Proportion in music best understood as the relationship between the amount of musical material in a song and the length of time that the song goes for. By ‘musical material’, I’m referring to the unique ideas – not counting repeats or slight variations. Another way of thinking about proportion is as the amount of variety in the song. There has to be a balance – too little variety will result in the listener getting bored and too much variety will result in the listener getting confused.
With too little variety, a song will have too much repetition. This is a common problem among beginner dance music composers. You’ve probably heard it before – a seven minute track that only has eight bars of music in it. It’s just different variations and combinations of the same material.
If you’re working on a track like this, you probably have very little source material and you’re trying to squeeze it for all it’s worth. The most effective solution will either be to introduce some more original material (not just variations or developments of what’s already there) or reduce the total length of the track.
With too much variety, a song will have too many different ideas, with little connection between them. You’ve probably heard this as a song that has a lot of good ideas in it, but seems to have a weak identity or doesn’t seem to have anything that binds it together. Instead of being heard as a single focussed piece of music, it comes across as a collection of different ideas.
If this sounds like one of your songs, you probably need to separate the ideas out into two or three (or more!) individual songs. Focus on getting more mileage out of fewer ideas. By varying and developing fewer ideas (instead of simply adding more fresh ideas) your song will sound much more focussed and cohesive.
Of course, the goal is to find the right balance. This is where judgement and experience play such an important role, and why it’s important to listen for proportion in your own music and others’ music. Try to identify when you’re listening to music that feels like it’s repeating itself a bit too much (like a sense of not knowing how long the song will go for) or when you’re listening to music that keeps switching between different ideas (like switching the TV channel or radio station).
There’s no magic ratio here. It depends on your personal taste and your listener’s expectations. Listen to a lot of music and you’ll know it when you hear it.