Well, Elgarian, not to rehash a previous discussion, music will always elicit a subjective experience. My experience of listening to music will differ from yours in so many ways. You will like composers I don't and vice versa. You wil like certain works that I don't and vice versa. Neither of us would be inherently incorrect in such a case, just different.
Though music like Tristan und Isolde may contains moments of extacy, there is also agony. Yes, one may feel agony as a result of being touched by the music, but the experience of being touched like that "feels good," somehow, even though it makes you feel sad. It's this feeling of being connected to something on a higher plane of existance that I find fulfilling, addicting, and sure...entertaining...dare I say fun. I mean, if it really did make you depressed and devestated beyond repair, I don't think anyone would listen.
I think it's the same principal as attending a sad movie or play. While the subject matter may be down-right depressing, we still go to the movie or the play to be entertained in some sense. No one ever says "I like going to the movies because it makes me want to kill myself," but rather, someone who goes to the movies often probably does so because s/he enjoys the experience, though s/he is not always seeing the most up-lifting stuff.
This is how I feel about music. Music can be profound, life-affirming, life-changing, terrifying, mystifying, tear inducing...all of that. The agony and the extacy. But being psychically connected to these sounds in such a way that causes these various emotions is, again, quite stimulating, and thus, an ejoyable experiece. It is the exciting experience of being taken somewhere very far from your mundane life. Well, my mundane life, anyway.
That's the last I'll say on this so I don't go too off topic, but perhaps I have articulated myself better this time around.