In response to my recent post on the neuroscience of musical predictions, Alex Rehding, the Fanny Peabody Professor of Music at Harvard, wrote in to offer a musical theorist perspective. He makes several excellent points, and complicates the neuroscience in useful ways, so I thought I’d reproduce the relevant parts of his email below:
The point you raise in your latest posting — about expectation and prediction — is one that has fascinated music theorists pretty much for the last 200 years. I realize that yours is a science blog, and I’ll try my best to resist the urge to add too many traditional music-theoretical talking points.
There is one interesting problem with this model, though, that has generated some interesting discussion in the music-theoretical world over the last twenty or so years. If we derive pleasure from anticipating potential connections – and especially being surprised by thwarted expectations – then it becomes difficult to explain why we would want to listen to a piece more than once: the novelty factor wears off, the uncertainty factor becomes less pronounced. In principle, the piece should get less interesting each time we hear it. Experience, however, shows that this is not the case: we greatly enjoy re-hearing familiar pieces. The whole recording industry makes a lot of money on the basis of this phenomenon.
Personally, I’d frame the discussion slightly differently. (And please take my views with a huge grain of salt. I’m a lay listener, not an expert.) I think our inexhaustible need for new music – we want the latest Rihanna radio hit – demonstrates that, once we memorize a piece of music, it grows a little stale. The essential surprise is drained out of the notes, so that there are no subtle patterns left to learn. And that’s when our attention begins to wander, and we buy the current pop phenom on iTunes. While there are certain songs I will be listening to forever – most of Blonde on Blonde, late 70s Bruce, Astral Weeks, Otis R., a few Pavement songs, Wilco, a little Bright Eyes, etc. – I’m always struck by the short half-life of most of my music. The stimulus goes from intoxicating and enthralling to tired and tedious in a few short listens. And so we keep on consuming, searching for another shot of acoustic excitement. I think the recording industry makes a lot of money on this phenomenon.
We can now see the neural anatomy that makes this cultural learning possible. The auditory cortex, like all our sensory areas, is deeply plastic. Neuroscience, stealing vocabulary from music, has named these malleable cells “the corticofugal network,” after the fugal form Bach made famous. These contrapuntal neurons feed back onto the very substrate of our hearing, altering the specific frequencies, amplitudes and timing patterns that our sensory cells actually respond to. The brain, in other words, tunes its own sense of sound, just like violinists tune the strings of their instrument. One of the central functions of the corticofugal network is what neuroscience calls “egocentric” selection. When a pattern of noises is heard repeatedly, the brain memorizes that pattern. Feedback from higher-up brain regions reorganizes the auditory cortex, which makes it easier for us to hear that same pattern in the future. So when we get sick of the latest top 40 jingle playing on the radio, these are the cells to blame. Their infinite capacity to learn means that we quickly get bored.
This, of course, raises the larger question of why certain pieces of music don’t go stale. Why are we still listening to Bach’s fugues, or Beethoven’s symphonies, or Kind of Blue? What is it about these particular soundwaves that allows them to evade the corticofugal boredom? I’d suggest that their place in the canon is inseparable from their ambiguity – their ability to encourage a multiplicity of interpretations – so that new listens reveal new elements to listen for. In other words, we are continually surprised by their sounds, by the capacity of the music to subvert our expectations. Frank Kermode famously argued that literature worked the same way: What makes a novel or poem immortal is its complex indeterminacy, the way every reader discovers in the same words a different story. The same book manages to inspire two completely different conclusions. But there is no right interpretation. If there were – if there was only one way to read Hamlet – then the words would be far less interesting. The art that endures is the art that never loses its capacity to surprise.
I think Professor Rehding makes another essential point in his discussion of rhythm:
The other point that I think is quite important in this respect — and that’s one that most music theory traditionally ignores — is the importance of rhythm and pulse. We don’t simply yearn for the eventual return of the tonic, but we want it to fall in one particular place (or a small range of places) within the temporal order of the piece of music. Composers generate a lot of tension by carefully manipulating the temporal features of their music: a musical climax is not merely about writing loud music but also about the careful gradual build-up and the decline afterwards.
This idea is an even more urgent given current musical trends. Over the last few decades, popular music has been transformed by its rhythms, so that some rap songs consist of nothing but words propelled by a pulse. Why is this so exciting, at least for the auditory cortex of people under 25? Does rhythm also take advantage of our musical prediction machinery? Or is it a kind of acoustic scaffolding, making it easier for us to follow the subtle patterns in the rest of the song?
I won’t even venture a bad guess to those questions. But I want to thank Professor Rehding for his feedback and comments.