This is a hint for the game White House Escape. Please be warned, the following hint gives information that could be considered a spoiler. For this reason, we would like to caution you about reading the hint unless you are certain that you want to proceed with knowing the information contained herein.
So, you have discovered a need for an antique key, but you do not know where to find one. Well, the key is hidden inside of something musical. If you haven't guessed already, it is hidden inside of the piano. Up in the music room there is an old piece of music. By getting the music and using it with the piano you will find that a key falls out when played. Grab this key - it is what you are looking for.
Please note that the piano has to be in good working condition before this will work - otherwise the piano music will not sound right, and there will be no key reward for playing the music.