update readme with noise effect and build notes

README.md

@@ -4,10 +4,29 @@ connor's rancid audio plugins. LADSPA.
 
 alternatively, chocolate recipes are powerful.
 
+## plugs
+
 ### crap_eq
 
 multiband parametric EQ. try redefining BANDS.
 
 ### crap_eq_const
 
-simplified code for a response defined at compile-time.
+simplified code for a static response.
+one day, this will be faster with compile-time constants.
+
+### crap_noise
+
+white noise generator. loud, full-range, 0dBFS. don't say i didn't warn you.
+
+## build notes
+
+`make` it. optional `bench` benchmarking target, doesn't build on Windows.
+
+if you're using gcc, try `CFLAGS='-O3 -ffast-math'`.
+`-march=native` actually seems to degrade performance slightly, but YMMV.
+
+if you're using clang, (at the time of writing this)
+you can't tune performance that much so just use `CFLAGS='-O2'`.
+
+can be cross-compiled for Windows for use in Audacity or a LADSPA wrapper.