The Ride of the Valkyries is the music heard when the rockets launch at the REPCONN test site at the end of the quest Come Fly With Me. It can also be heard on Classical Radio in Fallout 4 and Fallout 76.
"The Ride of the Valkyries" is not the actual title of the music, but is the popular name for the beginning of Act III of Die Walküre, the opera by Richard Wagner. This song is also featured in a well-known scene from the film Apocalypse Now.
With the console command TLC to turn off clipping, "Launch Music" is also a terminal that can be conversed with at the REPCONN test site. Find the room with the collapsed floor and three chalkboards. Find the chalkboard in the corner that has the desk and filing cabinets next to it. No-clipping through the wall will reveal a terminal that you can talk to, but all it says is, "What do you need?", and the only response is "Time for me to go."