"I have heard it said that "Art" is anything that invokes a response by the person observing it, is it the same kind of thing with music?" Just a response first of all to this quote. Art is a one off, unique object, subject, etc. produced through the creativity of author/authors expressing ????? who knows? A response is something quite separate and it is inevitable there is response to art (I can't quite put the capitol there).   It appears that we are talking about two things 1. the production of a song as a unique and individual expression by a person/persons and, 2. the response to the song.   Is that where the judgement lies?   "Ya like it" to quote someone else here, is probably as good as it gets???