In Nancy Drew: Message in a Haunted Mansion (MHM), Nancy tries to unlock the piano doors. To do this, she must view the sheet music in the attic desk, read the highlighted 5 notes (two books in the library will help identify the notes and which piano keys to play) and play BEGAG.
If you are unfamiliar with sheet music and reading notes, there are 2 books in the library that will help. The Theory of Music is found on the shelf to the right of the desk. It shows where the notes are on the sheet.
To learn where the notes are on the piano, find the book The History of the Piano in the library. It is on the shelf to the right of the two chairs sitting area.
