The Rules for Making Literature, Music and Pictures
The arts of the musician, the painter and the writer are essentially the same. In composing a fugue, after you have exposed your subject, which must not be too unwieldly, you introduce an episode or episodes which must arise out of your subject. The great thing is that all shall be new, and yet nothing new, at the same time; the details must minister to the main effect and not obscure it; in other words, you must have a subject, develop it and not wander from it very far. This holds just as true for literature and painting and for art of all kinds.
No man should try even to allude to the greater part of what he sees in his subject, and there is hardly a limit to what he may omit. What is required is that he shall say what he elects to say discreetly; that he shall be quick to see the gist of a matter, and give it pithily without either prolixity or stint of words.