[It sounds like she did have fun in a sense, despite it being "merciless," so there's a slight smile on his face as he responds. It makes sense, since music is clearly her passion, but he would like to encourage her to expand her horizons. his methods with Kaede didn't exactly work out but let's not talk about that, ahem]

It's worth a try. And even if I don't know much about tracking myself, I can try to be your new drill sergeant, if you want. [He winks playfully, because that's just what he does. I'm sorry.]