Agathas Quest

Shortly after entering Vault 92, you should come across an area with a few doors. I believe if you can pick average locks, the left path is pretty much a B-Line right to the violin. (NOTE: Be ready to fight a lot of mirelurks. That means get your shotguns and assault rifles ready.) Fight through Sound Testing until you get to a staircase going down. Be cautious, as there are two Mirelurk Kings at the bottom. You'll soon come across a room that you can't gain entrance to. Loop around to the other side and you'll see the violin through the glass. Access the terminal on the table and use it to unlock the door. Now, go back to that door, open it, and grab the violin and leave. If you can't lockpick average doors, take the door straight ahead and loop around to sound testing. A longer path cross past more mirelurks, but basically the same thing. Once you're done, return to Agatha and you will be rewarded with the frequency of her radio station, and if you find the sheet music in the vault or somewhere else in the wasteland and give it to Agatha and ask for a reward, she will give you her husbands old pistol, the Blackhawk.

Hope this helps.

There is a music sheet in the vault or at Springvale Elementary. You have to give her the violin and find her sheet music to get Blackhawk.

It is in the recording studio.