Full Idea
According to the Romantic theory music was an expression of something, of an idea (Hegel), of the Will (Schopenhauer), of 'intuitions' (Croce), or of feelings (Collingwood).
Gist of Idea
Romantics say music expresses ideas, or the Will, or intuitions, or feelings
Source
Roger Scruton (The Nature of Musical Expression [1981], p.54)
Book Reference
Scruton,Roger: 'The Aesthetic Understanding' [Methuen 1983], p.54
A Reaction
Deryck Cooke was the culmination of music as expression of feeling, and Stravinsky was the greatest rebel against the whole idea of expression in music. You can set out to create interesting music which does or does not grab the emotions.