One aspect of Cleveland rapper Kid Cudi’s soul-baring music that’s always stood out is his hums. An early example is “My World” from Cudi’s debut album, 'Man on the Moon: The End of the Day,' and he only stepped up the frequency of his humming from there. To gain insight into why Cudi’s hums—and humming in general—evoke a visceral response, Genius spoke to Dr. Suk-Jun Kim, a composer and senior lecturer at the University of Aberdeen in the United Kingdom who authored the 2018 book, Humming.