I think you need IOS 222/223 not 232 but I could be wrong. If you are running game through usb loader you probably just need to install Hermes 222/223 installer.
GAF's Wii Homebrew Tutorial: Hermes' Ios222/223
*** I might be wrong since I don't have any instruments for the Wii but if it is just like guitar hero then that is what you need.
As far loading from disc I have no idea.