[Coldsaturn]

You can also listen to it in game, when you go in the cafè to interact with the boys, on the right side of the page you'll find all the little buttons to change their clothes and the cafè background, and among them there's the button to choose the background music. You can scroll down past the tracks you have (and thus can select) to reach the ones you still have to unlock to listen to them. When you tap on the title it will also tell you how to unlock them.