K.K. Country
From Nookipedia, the Animal Crossing wiki
"K.K. Country" (けけカントリー) is a song by K.K. Slider. It has a lively country guitar playing through the whole song and a country drum kit. It fits the theme of a chicken egg farm, corn fields, or obviously the countryside (hence its name). The song is similar to the background music in Mario Kart 64 in the course Choco Mountain. The album cover depicts K.K. Slider sitting in a wagon inside a barn, and several villagers that include Bunnie, Groucho, Del at the entrance, with Butch and Buck overlooking him.
Jambette, Kiki, Victoria, Kody, Sydney, Goose, Belle, Ava, Drift, Maggie, Cookie, Cashmere and Ursala all play this song if they have stereos in their houses.