The only kind of nerd that can actually impresses you with their skills.
"woah that guy's so good at guitar! he must be a music nerd or something"
A person or a friend who is heavily in to music They listen to music all the time and you can't always talk to them because they are in their own little world.
Some play an instrument like the piano or trumpet. After they play one song they know it by heart. They are often kind people when you talk to them, but you mess up a song and they will go ballistic. They wear over sized glasses or just plain glasses and are always out of style.
Girl: "Did you see him?! He played so well."
Guy: "Yeah I saw him and he's a music nerd, I mean look at those glasses."
Girl: " I guess he is nerdy with those glasses on."