I just got a look at the GUI for the H3000 Harmonizer plug-in (thanks for the email Eventide).  It is fine until you get to the internal routing, which the GUI represents as a nightmare of crossing wires.  

It could have been much better – like the attached screenshot of Audulus, the beauty of which is that you can drag and move around the various audio algorithms so that the signal chain is intuitive, easy to see – and creativity-inspiring.  Just imagine any audio source or instrument in place of the keyboard…