Why do songs sound better the more we listen to them?

We put this to Adrian North, Professor of Psychology at Heriot Watt University, Edinburgh...

The reason why people seem to generally like music, or one of the reasons, is to do with the level of complexity in the melody.

By complexity we mean how erratic the melody is, or how varied the melody is. Basically, how "weird-sounding" the melody is.

For example, all the modern classical music, to many people, would sound quite weird, quite complex. Whereas a lot of modern dance music has got a fairly repetitive melody and so a lot of people regard modern dance music as being low in complexity.

We know, in the grand scheme of things, that people like moderately complex music - music that chops and changes a little bit, but not too much.

That's got big implications for how music fares when it's repeated. When you hear a piece of music the first time you don't really know what it's going to do next. When you hear it the second time you have a better idea of what it's going to do next. When you hear it the third, fourth, fifth, sixth, seventh times then you start to have a very good idea how that melody's going to progress. The more often you hear a piece of music the less complex it seems to you.

What that means is a piece of music that was originally too complex for you when you hear it a few too many times becomes moderately complex and you start to like it.

Conversely, a piece of music that was moderately complex and popular the first time you heard it, because you've heard it more times, becomes simpler. Now it becomes too simple for you and you don't like it any more.

In other words, liking for music is determined by complexity but complexity decreases with the number of times you hear a piece of music. That change in the level of complexity changes how much you like the piece of music in question...