When we think about the reality of meeting an extraterrestrial race, we often think about the difficulty, and sometimes supposed impossibility, of communicating or even recognizing that communication was being attempted. We wonder, also, how we could recognize a culture completely outside of our frames of reference. Could we even identify alien artwork, let alone appreciate it? Could we recognize alien music, if they indeed had a concept of music? A paper published in the journal Scientific Reports suggests that humans would be able to recognize and appreciate alien music due to our ability to process language, provided that it follows a couple of rules, and suggests that we might have an easier time understanding a completely alien culture than we've previously thought.
OK, music nerd time. Sorry. The rules in question aren't specifically musical rules, or even specific grammatical rules, but sort of "meta rules" of structure and coherence. Alien music would need to be built on local and non-local dependencies. Dependencies, in terms of music, are the commonalities that make a song sound like one coherent piece. A local dependency binds two adjacent things together—something like a drum pattern repeating every four bars—and non-local dependencies bind non-adjacent things together. Non-local dependencies can be understood in terms of pop-music: the classic verse-chorus structure. The two verses are non-adjacent, because they're separated by a chorus, but the second verse follows a rule set up by the first. This is used to create anticipation, resolution, emotional resonance and all the things that make music awesome. It's not confined to pop-music at all, you'll find local and non-local dependencies throughout all human music from classical, to punk rock, to non-western music like that from India or the Arab peninsula, that use completely different scales and rhythmic figures, but pop's simplicity makes it a very easy example.
Right, got that out of my system. That explanation is important, though. Essentially, as long as alien music had some sort of internal structure, we'd be able to recognize it even if it followed exactly zero musical rules that our culture had prepared us for.
To figure this out, Vincent Cheung and his team at the Max Planck Institute for Human Cognitive and Brain Sciences wrote some "alien" music of their own. Their description of the alien music is "randomly generated combinations of tone-triplets that were combined in a palindrome-like manner." They brought in musicians of different levels of expertise and played for them their "alien music," in a composition alongside random sequences with no internal grammatical rules. The musicians were tasked with determining which sequences followed randomly generated grammatical rules local dependencies, and which sequences had no grammatical rules. The team found that they could, and that they could identify non-local dependencies within the compositions as well.
Repeating the tests with the musicians in an MRI machine, the team found something surprising. An area of the brain on the right hemisphere was lighting up, which mirrored "Broca's area." Broca's area—named for anatomist Paul Broca—is part of the cerebral cortex on the left side of the brain and it's responsible for our understanding of dependencies in language. It's what flips out when you hear grammatical mistakes in language. What the researchers found is that we have a twin area on the other side of the brain that understands grammar in more ethereal and subjective things like music. It seems we might be hard-wired to understand structure itself, regardless of our cultural frameworks.
There are so many works of fiction that deal with the obvious communication and cultural barriers that would be between us and any alien species. The 2016 film Arrival, and the short story it was based on, dealt with that question and cast a linguist as the hero figure who deciphers an alien language that doesn't even conform to our sense of time. Close Encounters of the Third Kind involved communication through music specifically. It seems reasonable to imagine that any species that can travel through space would base their culture and communication on some internal set of rules, even if it doesn't resemble ours in the slightest. This research could suggest that we'd be able to easily recognize that there are rules, not just chaos, which would eliminate the very first barrier to understanding.
Of course, we already know what alien music sounds like.