Music expresses, say, "heartbreak." It doesn't express, "the heartbreak you felt two years and a month ago, on that rainy Wednesday when...."
Its essence, according to Schopenhauer, is to get to the essence, to leave aside the accidents.
"Precisely this universality, exclusive as it is to music, together with the most exact precision gives music its high value as the panacea for all our suffering. Thus if music ties itself too closely to words or tries to model itself on events, it is trying to speak a language that is not its own. Nobody has avoided this error as completely as Rossini; which is why his music speaks its own language so clearly and purely that it has no need of words at all and retains its full effect when performed in instruments alone."
That sounds rather equivocal praise for Rossini, who composed for opera, i.e. specifically for words and a stage set, not the concert halls Schopenhauer seems to have in mind here.
Still: here's a link to the William Tell Overture. You can decide for yourself if gloomy Arthur got or missed the point.
And that is the protagonist of that opera, portrayed above.