King K.K.
From Nookipedia, the Animal Crossing wiki
"King K.K." (けけだいみょう, K.K. Daimyō) is a K.K. Slider song. It is somewhat sad and has a dumbek drum, a santoor, and chimes all played in a very simple, downbeat tempo. Annalisa, Bill, Genji, Sterling (in Animal Crossing: City Folk), Snooty and Toby (in Animal Crossing: New Leaf - Welcome amiibo) have this song playing in their houses when they gain a stereo. Jay, Biskit, Felicity, Lily and Lolly are featured on the album cover.