K.K. Tango
From Nookipedia, the Animal Crossing wiki
"K.K. Tango" (けけタンゴ) is a K.K. Slider song, named after the dance (the Tango). It has a guitar playing a steady beat all the way through the song. Friga, Mira, Pashmina, Freya (in Population Growing) and Emerald play this song in their houses.
Beardo and Freya feature on the album cover, dancing the Tango. K.K. Slider is in the background playing a bandoneón.