I'm a composer and I'm wanting to find out whether a professional oboist can produce 'less pure' tone colors when they play - I'm after something that has the harshness of say a Shawm - would this be achievable say with a harsher reed, or is it generally something that a professional would not be that happy doing?

It is very easy to produce a harsher sound or different tone colors on the oboe. If you want a more primitive sound or a more ethnic sound, the oboe player can put more reed in his or her mouth and just blow with little control. I was at a concert recently performed by the Buffalo Philharmonic Orchestra. They played a piece from the movie Altered States. The composer was in the audience. Anyway, there were some very primitive sounds coming from the wind section. The piece is about hallucinations, so it was a very strange sound, but interesting. In spots, the oboe players sounded more like shawms. If you are ever able to listen to the piece you might see what I mean. It was written I believe by John Corigliani or something like that (not sure of the spelling).