Maurice Ravel (1875-1937) was a French composer strongly associated with impressionism (perhaps as much as Debussy, at least in orchestral repertoire) and early modernism. His most well-known pieces are probably his adaptation of Pictures at an Exhibition for orchestra, which is in fact far more popular and famous than the original piano piece; and Boléro, a piece consisting of a single melody repeated and amplified again and again, which is also very popular (the LPO is performing it literally as I write) but considered, both by Ravel himself and by music historians, to be a rather shallow piece.
Like Strauss, he took a more conservative, at least partially tonal approach to the more modernist pieces in his opus. His works always display a bit of Debussy's flavor--not always clearly tonal, but with complex, beautiful harmonies that occasionally resolve into more traditional tonal relationships.
A good example of his more modernist style is his ballet Daphnis et Chloe, published c. 1912. Now more popular as an orchestral suite, it originally portrayed a classical scene about the love between Daphnis and Chloe, their separation by various misfortunes, and their reunion by the god Pan. The Dionysian, pastoral, and fantastic setting is a definite step away from the early influence of Wagner (it seems like every composer loved Wagner on first hearing him, but eventually condemned him as simplistic, technically lacking, or misguided). We could also, at a stretch, say that it shows some influence of Nietzsche. Here is a recording of the piece as an orchestral suite:
Even more than most music, I think that the impression the listener gets from the music itself cannot be fully explained or conveyed by any analysis I attempt. The tranquil, mysterious harmonics, interrupted at intervals by sharp fanfares or with melodies laid on top, give the feeling of a great, unfathomable power at work, regardless of the capriciousness of some of the music. Ravel uses unusual effects to produce this ethereal quality; he fully takes advantage of the wordless choir, and uses the odd and disconcerting wind machine several times starting at 22:40. I think the emphasis on expression over form and the uncertainty and "partial" feeling of a lot the music are very modernist. They are also very impressionist--impressionism is in many ways an early expression of modernism, and this piece is a sort of threshold between the two.