According to one theory (assuming that extraterrestrials exist), musicic is “an ideal medium for interstellar communication”:
Each song in the Sónar messages is only a few seconds long and might only be called music in the loosest sense of the word. One track was created by feeding an algorithm music and letting it remix the notes as it saw fit, which resulted in something that sounds like a horror movie sound effect. Another uses the atomic numbers of a handful of oxygen, silicon, and other elements as the frequencies for pure tones. These arrangements don’t make for easy listening, but that’s not the point. Instead, the artists use music as a way of conveying information, whether it’s about our aesthetic sensibilities, our technology, or our physiology—all topics that would presumably be of interest to an extraterrestrial recipient.
In many respects, the Sónar messages are on well-trodden ground. The first human-made object to make it to interstellar space, the Voyager 1 spacecraft, carries a gold-plated phonographic record that includes Mexican folk music, early rock and roll, a Peruvian wedding song, and more. In 2001, a message sent from the Evpatoria radar in Ukraine included theremin renditions of Beethoven, Vivaldi, and Gershwin; a few years later, NASA blasted a Beatles song at a star 400 light-years away.
Daniel Oberhaus, “Why We Keep Sending Music to Extraterrestrials” at Slate
And, having discovered we like rock, they sent us Oumuamua, right? 😉
See also: Philosophy prof: Our theories steer us away from finding ET. Every so often the people searching for extraterrestrial life that just never seems to turn up need a pep talk. It often takes the form of “You know, we could be on the wrong track”.
and
Tales of an invented god: The most important characteristic of an AI cult is that its gods (Godbots?) will be created by the AI developers and not the other way around