Professor Layton always has ridiculous endings, but I think this pretty much took the cake. Everything from the giant robot on was ridiculous, especially Luke falling roughly four stories and landing on his back, totally fine, then channeling Tarzan to make his way up to Janice.
I loved it all though. :D
Nina knew the song because she had Melina's memories, if that's who you were wondering about. She didn't fully lose them until the end.
I don't quite understand how Melina had the third song, but I assume it has something to do with how they said she was possibly the reincarnation of the queen of Ambrosia. This is a series whose secondary protagonist can inexplicably speak to animals, after all.
I don't think she had the third song, rather it was the bass part to the organ/piano piece. At least that's what I thought! Lol.
I didn't mind the songs I thought that was a lovely idea. More the robot thing! That almost put me off. Good movie overall. A good example of good Anime.