Best friend keeps playing Minecraft parodies of songs. How do I stop him?

Tell him that sort of behavior is autistic and for children. Maybe request that if they do it, just don't do it in your presence. If that doesn't work, quit being their friend.

You can never stop steve B)

Stick a headphone jack in the speaker socket. It will drown out the noise.

Punch him in the throat… With your pinky.
while he is choking and coughing, burn his computer down.

Let them listen to what they want, and you listen to what you want.