..to change volume i just mess around with the LXDE plugin
It would be very helpfull not only draw a red frame around the symbol but also use the right mouseclick. The right mouseclick is the most important feature of the mouse.

If you did so, you'll get the option "Volume Controll" settings (alsamixer).

Read the manpage of alsamixer and try the effects with the keys F1 - F6 within this tool.