cannot find any information on how to use custom filters / real time sound generation in 3.5

the FAQ mentions that unity basic now has custom filters and real time sound generation but i cannot find any information about it in the manual and the audio source doesn’t seem to have anything new resembling those features

is there nothing available ? , if this is something controllable from the editor i cant find it.

This is documented in the scripting reference that comes with the installer:
You have to overload OnAudioFilterRead (float data, int channels).