At some point all music was "modern music" or music of its time and probably equally decried by parents.
When younger DD was exposed to our eclectic tastes in music and now we are exposed to hers. We share an iTunes account so what I have on my iPad she has on hers and vice versa. I love learning new music and she has surprising old tunes of mine on her playlists. It's all good. I have no fears of either of us being corrupted and we both live in hope that DH will have his tastes extended!
I wouldn't be too worried about the social currency aspect. Children take great delight in exposing their friends to the latest in thing. Your DC will like it or not and that in itself prompts an interchange between the kids. Once kids get older they develop their own tastes which may or may not intersect with those of their friends. Learning to accept that not everyone likes the same thing often starts with music!
