I will be entering the Masterprize, but this is a contest that is entered by guys that are already on there way to being in Groves dictionary!
Hey! Don't knock the modern until you've tried it! I would say that any of the composers here can do it! Some of the art music now is not so great because the composer is trying too hard to be "out there" but some is also really excellent. Try new things! With GPO you can. I could compose a 12 tone orchestra piece and hear it! I haven't seen a professional orchestra tackle one except very rarely.
Atonal music can sound good. It just takes more work. Listen to John Williams serious music. I suggest everyone check out his Violin Concerto and his Flute Concerto. Also listen to the 'other' music on his Star Wars soundtracks. You know, the stuff that's not blatantly major or minor. Starting with Empire Strikes Back he goes atonal in large sections of the score.
I believe some of the most expressive music is possible because you don't have to worry about whether a progression sounds right or not! Just compose the melody you want no matter what notes it has in it!
Every composer should start off writing for single instruments, then small chamber ensembles, etc. Write for winds before strings. Most composition professors will have their students compose one or several string quartets before composing orchestral music. This method is very good.
OK Sean, I am done with my speech. Thanks for your kind words and I will get to work posting the GPO string trio now!
DMA Student and Teaching Asst in Music Theory/ Composition at the University of Miami Personal Website