What is music? There's no end to the parade of philosophers who have wondered about this, but most of us feel confident saying: 'I know it when I hear it.' Still, judgments of musicality are notoriously malleable. That new club tune, obnoxious at first, might become toe-tappingly likeable after a few hearings. Put the most music-apathetic individual in a household where someone is rehearsing for a contemporary music recital and they will leave whistling Ligeti. The simple act of repetition can serve as a quasi-magical agent of musicalisation. Instead of asking: 'What is music?' we might have an easier time asking: 'What do we hear as music?' And a remarkably large part of the answer appears to be: 'I know it when I hear it again.'
Psychologists have understood that people prefer things they've experienced before at least since Robert Zajonc first demonstrated the 'mere exposure effect' in the 1960s.
It doesn't matter whether those things are triangles or pictures or melodies; people report liking them more the second or third time around, even when they aren't aware of any previous exposure. People seem to misattribute their increased perceptual fluency - their improved ability to process the triangle or the picture or the melody - not to the prior experience, but to some quality of the object itself. Instead of thinking: 'I've seen that triangle before, that's why I know it,' they seem to think: 'Gee, I like that triangle. It makes me feel clever.' This effect extends to musical listening. But evidence has been accumulating that something more than the mere exposure effect governs the special role of repetition in music.
To begin with, there's the sheer amount of it. Cultures all over the world make repetitive music. The ethnomusicologist Bruno Nettl at...