This does look like a very nice little game I could consider playing. I do have an ear for music, but only one!
On the face of it, it reminds me a lot of Opera Fatal, which was also a German game where you had to solve a musical mystery by learning about melodies, rhythms, keys, genres etc.
Interestingly, the trailer speaks exclusively of 'the child (who plays the game, solves the riddles)' etc.
No mention of any adults, so I wonder if it's elementary level. On iTunes it says 4+, but this may just refer to the level of violence or intensity of suspense.