The guards from noticing me when I try to open a door!

Hint 1 of 8:

You need to make sure that leave the hallway.

Hint 2 of 8:

Listen in to what they have to say.

Hint 3 of 8:

They need to find Cassima's nightingale.

Hint 4 of 8:

You don't have Sing Sing, but you do have a convincing replacement.

Hint 5 of 8:

Get the mechanical nightingale from the pawn shop.

Hint 6 of 8:

You have to be careful that the guards don't see you when you leave it.