Here's a really simple tone and volume control.
It works in a similar way to the tone/volume controls often found on portable music players.
To install new plug-ins, place them in the Plug-Ins folder inside the Audacity installation folder.
On Windows computers, this is usually under "Program Files".
On Mac OS X, it is usually under "Applications".
On Linux, create a folder in the Home directory and name it ".audacity-files", then create a sub folder called "plug-ins" and place the .ny file in there.
All operating systems:
Restart Audacity, then this Plug-in will appear underneath the divider in the "Effect" menu.