Stephen Hough, the British pianist, composer and writer, posted a couple of articles about whether one can be a musician and not compose and, conversely, whether one can has to be able to read or play music to be a musician. The articles are fascinating reading, as are the comments that follow.
Personally, I am not a composer. I haven’t really tried (since my forced “compositions” during my University Theory classes) but then, there is absolutely no musical thought in my brain or soul that has not already been written. I have a lot of respect and admiration for those who do and I quite like what Brahms had to say about the process:
“It is not hard to compose, but what is fabulously hard is to leave the superfluous notes under the table.”