When much of my day involved setting up playlists and rotations for a radio station in complicated music schedulers, we had to create dummy slots in order to help time out an hour to sixty minutes. We decided that the average length of a song was three minutes and 30 seconds, so that’s how much time we allotted to one of these dummy slots.
In all the years I worked with that number, it never occurred to me to ask why the average length of a song on a radio was 3 minutes and 30 seconds. Yes, there are plenty of exceptions, but if you took the universe of pop and rock in its totality, that’s more-or-less what you have to work with.
And it’s not just radio people. We’ve all become conditioned to accept that 3:30 is about the right length for a pop and rock song? That length just feels…right, somehow. But why? Why not two minutes? Or five? Or ten?
One theory relates to the maximum amount of music that could be stored on physical media. You’d do well to get three minutes on an old Edison cylinder. The best anyone could do with an old 78 was four minutes. And while you could squeeze up to seven minutes on the side of a 45, the physical limitations of the grooves pointed to 3:30 being that balance between storage and audio quality.
A nice idea, what about LPs? They were introduced in 1948 and can hold about 22 minutes per side. A CD can hold up to 80 minutes. And an MP3 can be whatever length it has to be. And if you check out this graph, you’ll see that songs have been getting longer.
It turns out that the answer may be a lot more complicated than that. A lot more. Take a look at this article in Wired.