Should work out the box, just launch the fla file, if your having problems look to flash security settings

Have a look at; 

http://www.tree-axis.com/Ess/_examples/inputFFT/inputFFT.pde << Processing
http://music.ece.drexel.edu/ALFdocs/files/DATF-as.html << Alchemy compiled c++ app with interface for AS3