if you search for a real sound it often shows you a lot of synthetic crap, i would be a nice idea to catoegorise the sounds in different parts of sections like synthethical sounds / real sounds / sub-category Nature etc.
This tip might help a bit.
If you search and put a minus sign in front of a search term you definately don't want then anything using that tag /description will be rejected from the search. In your particular case using say, nature natural fieldrecording -synth -synthethical -beat -drum -chord... etc. will certainly reject a lot of stuff even though it won't be a perfect filter. I think the problem is that because of the ad-hock open nature of tagging and different peoples ideas on the best key words to use no system is going to be perfect. I think the way it works now is pretty damned effective though.
I've not been here (at freesound) long and remembering and typing long lists of words is a pain in the a** for me so what I do, not just for freesound but for other things as well is keep a text file on my computer desktop with loads of pre written stuff including lists in it that I simply copy and paste as appropriate. The lists evolve in a darwinian fashion as they get used. Also avoids typos.