You won't be able to do that until almost the end of the game, so you can forget about it until then.
Hint 2
The combination is hidden in the music your mom used to play on the piano, as seen in Nancy's flashbacks. Later in the game, you'll have an option to ask your dad about that music.
Hint 3
He says he'll transcribe it for you; it'll take a while, so do other things and watch your hotel room door for an envelope.
Hint 4
In fact, you'll find it on your door when you return to your room after it was ransacked.
Now that you have the music, notice the sections of the music that have been highlighted. One is titled "Nancy," one is "Carson," and the last one is "Kate."
Hint 6
Notice also that the letters on the box are A through G. If you've ever studied music in any form, you know that musical notes are also A through G.
Hint 7
So the combination to the box could be the notes of one or all of those three sections of music. Read to the end of this hint for the right keys to press.
Hint 8
Let's try it out. Enter the Nancy section of the music (if you don't read music, you can use the bagpipes book to find out what each note is), and one light turns green. We're on the right track!
Hint 9
The Carson section turns on the next light, yay! But something is different about the Kate section.
Hint 10
Oh, right, it's in the bass clef, isn't it? That is, it's played on the lower notes on the piano, the ones the left hand plays. That means it uses slightly different notation.
Hint 11
You'll need to get all three sections of music right in one go. If you save the game and reload, or if you back away from the box, it resets and you have to start over.
Hint 12
Here are the letters you need to push on the box to open it. (Note that this won't work until you've gotten the music from Dad; in fact, you can't even look closely at the box until then.)
Buy me a coffee