Who composes orchestral music today?
Many composers still compose music for orchestra! Perhaps not many do it professionally, but, many excellent composers are otherwise employed as university professors, or as bankers. I know some!
This is going to sound funny, but the problem is not a lack of composers; the problem is the orchestras. It is no one's job to review incoming scores. I'm serious! Any professional orchestra probably has a mountain of new compositions piled up on a desk somewhere, but it's no one's job to review them, so no one does. Money is always tight in the music industry, and these orchestras are not about to employ more people to do more stuff when they're already struggling.
That said, I'm with you- I think *I* *should* be in the prime demographic for my local orchestra, but they play a lot of old music. I'm interested in personal creativity, and there isn't much room for that in an orchestra, but there is always the creativity of the composer to enjoy. I wish my local orchestra would put a world premiere on every concert, or have one concert per year of all premieres. But the orchestra is a business, and they are not interested in experiments or undue risk. They will play new compositions, but only those that have already proven themselves.
There are organizations dedicated to premiering new orchestral repertoire, notably the American Composers Orchestra. They are not the neighborhood symphony, however.
I wish the local orchestra performed more new music. They do *some*, but not nearly as much as I'd like. The artistic director did bring the orchestra back from the brink of bankruptcy back into profitability, and I respect that. She has a mountain of honorary doctorates, and I respect that. But when I do go to orchestra concerts, the average age is "deceased," and I can't help but think that they need to do a lot more to stay relevant. It's a brilliantly talented group of performers, but they have no control over their orchestral careers. They just show up and play when they're told. They've been making recordings. They're going back to Carnegie Hall. But I have this nagging thought that I want so much more from my orchestra, and no one is going to give it to me.
I'd take this mission on myself, but I'm busy with other things, like writing rock songs. c'est la vie...