Hello,
I have no idea how to make audio expander with pd. I haven't noticed that object [compressor~] could work like it with parameter like ratio, like some of VST's does. I think of idea to feed expanded attacks of mixed music to [bonk~].
If somebody could share ideas about, pleas do so.

look at http://www.pd-tutorial.com/english/index.html
in chapter 3.9 there is an exercise to create an expander which suggests that if you understand this chapter you can do it
if not look in the solution

Thank you slur, I know this tutorial web, but didn't reminded then needed most. Thanks