The game is built around adds. You have to watch an add for every song, there are pop up ads on the menu and whenever you fail one of the ridiculously hard levels, it makes you watch an add to retrieve your progress. I do understand that you need ads to get revenue, but the amount in this app are ridiculous. They constantly promote their 'VIP' version of the game, which removes adds. Turns out, it is £6 a week. An absolutely ludicrous price. Could have been a good game, but ruined by developers.