Hello,
Is libxtract (still) available for Pd? This paper has an illustration of it:
http://www.scribd.com/doc/10150335/libxtract-a-Lightweight-Library-for-Audio...
Apparently it was announced on Pd list in 2006. But on the current LibXtract repository (https://github.com/jamiebullock/LibXtract) I can't find any reference to Pd.
Katja