Linguician beta is a recently launched language learning service that uses music to teach new tongues. Here gamification is used to teach new languages, much like Duolingo. However, the founders of Linguician want more gamification in their product, about 80% total. That means the majority of a user's time on Linguician beta will be spent listening on quizzes. Translations for lyrics are provided, and at the end of a song a multiple choice quiz is given. Correct answers earn a user LingoCoins which can be used to buy new songs.
Linguician beta was just launched, so its features are a bit limited. However, there are plans to implement machine learning so that users who progress in their learning can be challenged with more complex lyrics. Linguician beta is not available as an app, although it seems likely one is on the way.