For my senior thesis at Yale, I wrote about the neurobiology of music, exploring the question of what makes music sound good.

The paper dove into a slew of topics, from how the physics of musical sound waves aligns with the structure of our cochlea (the spiral structure of our inner ear), to how melodic phrases seem to hijack the portion of our cortical brain used to parse sentence structure.

One thing that stuck with me from my research is the way in which our enjoyment of a song depends on its balance of novelty and familiarity.

Consider a melody that repeats a phrase three times: ba-da-dum, ba-da-dum, ba-da-dum.

Now, what does the melody do next? It could honor the repetition of the phrase (ba-da-dum again), or it could move to something new (ba-da-doo-doo-da-dee-da).

And, basically, we like music best when it does what we expect it to do roughly half of the time, and then does something unexpected the other half of the time. In other words, we like music best when it balances familiarity and novelty in equal amount.

That, in turn, leads to some other fascinating ideas. For example, how much we know about a certain style of music can change how well we can predict what happens next in that kind of music, which in turn determines how much we enjoy it.

Think about jazz, improvisational music built around a complex set of rules. If you understand the structure of those rules, your expectations of what ‘should’ happen next is different than if you don’t know the underlying structure.

That helps explain why regular jazz listeners gradually develop a preference for increasingly complex styles (which they slowly build the ability to understand, and therefore predict), yet that just sounds like unpleasurably random noise (all novelty, no familiarity) to a novice set of ears.

I’ve seen the same thing in hip hop, which over time has developed increasingly complicated structure. Serious devotees find the best new MCs to be unbelievably skilled poets, writing dense, interlaced, and self-referential rhyme schemes that would make Shakespeare blush. Whereas more casual listeners basically just hear somebody talking quickly over a beat.

To that end, I’d highly recommend this great explainer video from Vox, which traces the evolution of rapping over the last three decades. It’s a fun, short watch, full of very clear explanation, that I think will give anyone a much deeper appreciation for what makes great hip hop so very impressive: