Audio sample processing functions

Hi all,

I am trying to make simple VST audio plugin. In order to that I will need some basic operation with audio samples, such as: mixing two channels into one, dividing sound into two channels (panning), HP/LP filtering, ADSR envelope, compressing, EQ and so on…
I know that some of these functions are not hard to implement and also that there are some code example apps such as peggy2000.
Do these classes and functions already exist in Juce or should I make it on my own?
If yes, which ones?
If no, could you recommend some other library to use?

I would prefer using already existing functions than making my own because they are written by professionals who understand matter much better than I do.

Thanks in advance.