When you start the game, go to the screen where you select your player and go to the phone to select "Reset Time". Set it to a time when K.K. Slider comes to the museum (between 8:00 p.m. to 12:00 a.m.) and start the game. After you get your song, go back, save, then go back to the player selection screen. Reset the clock again to the original time and once you start your game again, save and repeat those steps. Note: This takes some time.