have to take a piece of music an write it for string orchestra. was thinking of doing a double bass piece (but NOT a solo piece). anyone have any advice on this, any suggestions?
One sure fire way, maybe not the most creative, is to take a woodwind or brass quintet and transcribe it for string orchestra. You will have to deal with a few transpostions and/or range issues but it is really easy to pull off since it is written with that voicing in mind. I always got in to trouble in orchestration when I tried to reduce a big work or re-voice a work written for smaller ensembles.
A nice Bach fugue will work too, but you end up with more doublings in the parts. (ie. cello and bass)
Am I right in guessing that you're doing this for some kind of class? A good starting point would be to look at what you're expected to know about orchestration (what were you taught? what's on the syllabus?) and then consider what kind of projects would demonstrate that you've grasped that information?
It's good to be creative and original but you also want it easy for the teacher / examiner to sit down with their marking scheme and happily give you a high grade.
It's true that transcribing a wind ensemble piece would probably be fairly easy. But you'll probably learn more if you take a piece written for piano and try to reimagine it as a piece for string orchestra. Then it's more a matter of translating ideas rather than just transposing parts.
French impressionist piano music is a good source of music that would translate well.
For an easy project, you might try something from Bach's Art of the Fugue.
For a really interesting and I would think suprisingly tough project, expanding one of the Back Partitias for solo violin would be impressive if you pulled it off.