I've got (almost) rhythm

Music is one of the things thought to make us human, to differentiate us from animals. If you've ever heard a piece of electronically generated music, you can tell in an instant. The beat is too regular, too perfect. It's a little unsettling. Researchers in Germany have been looking at the flip side: what makes music human?





Actually, a lot of electronically produced music does have imperfections baked into it, to make it sound more human. "White noise" is added, random deviations from the beat. One note is a little too soon, the next is really late, and so on.

But, as the research team discovered, the natural human deviations aren't purely random. They studied the rhythm of human subjects in two tasks: drumming and voice performance.

Both types showed "pink noise" type variations, meaning that if you were a little too early on the first note, you're more likely to be a little early on the next note as well. Eventually you will "forget" about the first note, and be just as likely to be early or late.  It's all still pretty random, but less so than white noise.

The drumming was less random than the voice, displaying almost perfect "1/f" behavior. [I won't delve into the math.]

To further investigate this, the researchers produced two electronic versions of the same music, and added white noise  rhythm deviations to one sample, and "1/f" deviations the other. Subjects preferred the "1/f" version. You can try it out.

It remains unclear why we prefer this sort of noise - why would this have evolved? Why do we care about deviations? Shouldn't perfect rhythm be preferable?

Another question is the timescale, the average human deviation was on the order of 10 milliseconds. Why is this pleasing?

This "1/f" noise shows up a lot of places. It has actually been shown to exist for two other aspects of music: pitch and volume. Heart beats and neural signals have been shown to display it. It's present in electronics as "flicker noise" and can be used to describe phenomena in economics and meteorology. It's unknown whether this is all the reflection of some universal truth, but it's speculated it may be.