You said: "It’s like asking the question, "Am I in pain?" That’s not a question I can make sense of without some kind of science fiction scenario." Can you elaborate on that paragraph? I don’t understand what you are trying to say.
The OP asked for someone beside himself how he could know if he was enjoying music. I said, that’s like asking someone else "Am I in pain." That sentence does not make sense to you. It doesn’t make sense to me, either. That’s why the equivalent sentence, "Am I enjoying my stereo?" is equally senseless. It’s an ill-formed question and cannot be answered. See, SEP, e.g. to read more.