[Goku can be a noisy kid. He can't help it, he's also easily excitable and everything is just like so new to him. Music is specially new, but still he can be quiet and still sometimes. Now is one of them. He will just listen with his whole attention fixated on Vash and the music that comes from the harmonica. Concentrating really hard, as if trying to memorize it because he wouldn't hear it again.
There's a big smile on his face though, clear sign of him enjoying it.]
[Action]
There's a big smile on his face though, clear sign of him enjoying it.]