here is the long explanation:
-=PART ONE=-
-browse to your fallout 3 folder, using the explorer
-go to the subfolder called "Data" inside the fallout 3 folder
-create a new folder called "sound" inside the "Data" folder
-go into the newly created "sound" folder, and create a new folder there called "songs"
-again go into the "songs" folder you just created and create a new folder with the name "radio"
-go into the "radio" folder and create the folder called "violin"
-=PART TWO=-
-choose up to 12 songs you would like to hear
-rename those mp3-files each to one of the names at the end of this post
-copy your mp3-files into the "violin"-folder you created in the last step of -=PART ONE=-
-=PART THREE=-
-start the game and finish "Agatha' Song" quest
-use your "Pip Boy 3000" to tune into "Agatha's Radio Station"
-=SHORT WALKTHROUGH=-
to finish "Agatha's Song" do as follows:
-travel up to the most north-eastern corner of the capital wasteland
-find "The Republic of Dave"
-from there tavel straight west until you find "Vault 92"
it's about a 1/4th of the full distance from the east-end to the west-end
other locations near "Vault 92":
-"Old Olney" is a short distance about east of "Vault 92"
-"Greener Pasture Disposal Site" is south of "Vault 92" and allmost as far away from "Vault 92" as "The Republic of Dave" is
-"Clifftop Shacks" is west of "Vault 92" and as far away from there as "The Republic of Dave" is
-enter "Vault 92"
-!IMPORTANT! there are Radroaches (not dangerous), Bloatflys (a bit more dangerous) and Mirelurks (very dangerous) in there! make sure you are equiped to fight those!!!
-NOTE: if your hacking-skill is good enough, hack the computer terminals that are on the walls all over the place. if you find one with "Sound Flush" or something like that in the menu, use it. it kills the mirelurks instandly. but i dont know if it kills all mirelurks in the entire vault.
-search the vault until you find a studio. the door is locked, but can be unlocked via a computer in the room next to it. the violin should be in the rear lefthand corner, if you look at the room standing in the door.
-travel to "Agatha's House" located allmost at the center of the capital wasteland. its surroundet by rock-wall and you can only enter it via a bridge that is located to the south.
locations near "Agatha's House"
-"Germantown Police HQ" is allmost north from "Agatha's House"
-"Minefield" is north-east of "Agatha's House". the distance between "Agatha's House", "Germantown Police HQ" and "Minefield" are allmost the same, so those three locations are in a allmost prefect triangle standing upside down
-"Scrapyard" is a medium distance to the east of "Agatha's House"
-"Meresti Trainyard" is a very short distance to the south-east of "Agatha's House"
-"Big Town" is south-west of "Agatha's House" a bit farther away than the "Scrapyard" is
-"Hallowed Moors Cemetary" is a medium distance to the west of "Agatha's House"
-enter the house and find agatha.
-talk to her. one of the dialog branches is about her living alone and only a few caravans visiting her about once a week. she "pays" the caravans with the music she plays on her hand-made violin, but she could play much better on a real one. tell her you can get it for her. about then should be a dialog option available that you allready have it.
-the quest "Agatha's Song" shoud be finished as you leave the dialog.
-leave the house, and you should receive a message, that "Agatha's Radio Station" is now available to you.
NOTE TO THE WALKTHROUG: i wrote this guide entirely out of my memory with help of a very crude map that can be found here:
Link"Vault 92" is location "09" on that map, "Agatha's House" is location "31".
so i can't guarantee you that the locations are exactly where i sayed they would, but im pretty sure they are.
-=MP3-FILE NAMES=-
they now are typo-free!
the names are:
mus_violin_noodling_01_radio.mp3
mus_violin_noodling_02_radio.mp3
mus_violin_noodling_03_radio.mp3
mus_violin_noodling_04_radio.mp3
mus_violin_noodling_05_radio.mp3
mus_violin_noodling_06_radio.mp3
mus_violin_partitano3gigue_bach_radio.mp3
mus_violin_partitano3p_bach_radio.mp3
mus_violin_sonatano2grave_bach_radio.mp3
mus_violin_vc_1stmov_dvorak_radio.mp3
mus_violin_vc_2ndmov_dvorak_radio.mp3
mus_violin_z_sarasate_radio.mp3
i think thats about as much explained as i can.
if i missed something or you need more help, please post the questions here.
i hope i helped. =)