Full Idea
The 'expression theory' holds that if music is sad that is because it expresses the composer's sadness, ...but composers take a long time composing sad works, and may even been gleeful at receiving payment for it.
Gist of Idea
It seems unlikely that sad music expresses a composer's sadness; it takes ages to write
Source
Stephen Davies (The Philosophy of Art (2nd ed) [2016], 6.4)
A Reaction
[compressed] Pretty conclusive. I see composing as like acting. Just as you can put on a happy or sad face, so a composer can discover music that feels sad or happy. Three movement sonatas don't fit expression at all.
Book Reference
Davies,Stephen: 'The Philosophy of Art (2nd ed)' [Wiley Blackwell 2016], p.143
Related Ideas
Idea 20404 Music isn't just sad because it makes the listener feel sad [Davies,S]
Idea 20405 Music may be expressive by being 'associated' with other emotional words or events [Davies,S]