The singing is the best part. Courtnee has a great voice.
I LOVE her voice. About her singing, dont know if its really spoiler but still:
the scene where Booker plays the guitar and Elizabeth sings to that poor child is soo cool ;-; Specially because it comes in a very intense part of the game. Its like a breath of fresh air.
I also noticed in the credits that Courtnee sings it and Troy Baker (Bookers VA) actually played the guitar.
