what's the fmod_studio.Bank's [userdata]?

I want to now what’s userdata contain? I need to get some byte about the music or event and so on.

How can I analyse the bank build by FMOD Studio?

The UserData is primarily used in case the user wishes to ‘attach’ data to an FMOD object.
It can be useful if an FMOD callback passes an object of this type as a parameter, and the user does not know which object it is (e.g. if many objects of this type exist). It is something you have to add to the bank by using Studio::bank::setUserData.