The symTone GUI is custom built to handle dual-cursor interactions. This means that program functionality is accessed via popup, transparent, hierarchical menus that can be invoked with either middle mouse button. This eliminates the handedness bias found in most GUIs: left-handed users can make menu selections with their left mouse and index finger and right-handed users can make menu selections with their right hand and index finger. No software tweaking is necessary.

 

At this point, file IO is still performed via the traditional carbon GUI, and thus the need for a third pointing device to control the system cursor in these dialogs. When Apple decides to support multiple cursors, this will go away!