While it appears to serve no function in Fallout: New Vegas other than having a value of 100 (same in both games), in Fallout 3 it can be brought to Agatha as part of the quest Agatha's Song. Your reward will be the Blackhawk or good Karma.
Vault 92: Found in the Living Quarters. It is in the bathroom of the men's quarters, inside the closed bathroom stall, on the ground next to the toilet.
Arlington Library: Found in the Children's Wing of the library, past the firehose box. Go right, past the Nuka-Cola vending machine. Enter the first room you see. The music paper is in the right cubicle by a music stand on the floor. If you look at the local map, it's in the upper of the two rooms on the left side of the map.
The National Archives: Found in the first room in the Archive Sub-Basement, when not entering from the lift with Sydney. The room is full of books and broken metal shelves; music paper is on the bottom shelf of the west wall.
Springvale School: Enter the front door of Springvale Elementary and turn to your right. You'll enter a hallway. Go to the first room (it should be right in front of you) and there will be a couple of mattresses and a flipped over desk. Walk around over to the desk and right behind it is a sheet music book.
Roosevelt Academy: Found in the Arts and Athletics hall on the stage near the music stands which are on the right of the stage. May be located on the roof of the small fake building to the right (closest to the music stands).