I have gone all through Brahms by now. All I can say of him is that he's a puny little dwarf with a rather narrow chest. Good Lord, if a breath from the lungs of Richard Wagner whistled about his ears he would scarcely be able to keep his feet. But I don't mean to hurt his feelings. You will be astonished when I tell you where I get more completely bogged down than anywhere else--in his so-called 'developments." It is very seldom he can make anything whatever of his themes, beautiful as they often are. Only Beethoven and Wagner, after all, could that.
[from a letter written by Gustav Mahler to Alma Mahler on June 23, 1904, and found in Irving Kolodin's The Composer as Listener]