Full Idea
To describe a piece of music as expressive of melancholy is to give a reason for listening to it; to describe it as arousing or evoking melancholy is to give a reason for avoiding it.
Gist of Idea
Expressing melancholy is a good thing, but arousing it is a bad thing
Source
Roger Scruton (The Nature of Musical Expression [1981], p.49)
Book Reference
Scruton,Roger: 'The Aesthetic Understanding' [Methuen 1983], p.49
A Reaction
Expressing sexual desire, while avoiding arousing it, is the nice challenge for a particular type of art. Would Scruton say that expressing joy is a good thing, but arousing it is bad? It is a nice observation, though.