I gave up on doing this inside csound, because of latency issues.  So I wrote
my own programs to do it.  If you use a Mac, you can try GrainWave (which does
this) or my upcoming release of an easy-to-use effects processor that emulates
having a box full of effects pedals.
-- 
Mike Berry
mikeb@nmol.com
http://www.nmol.com/users/mikeb