I think it is the Tone Stack Calculator, a free download here: http://www.duncanamps.com/tsc/
Very nice little app.
You´ll need Virtual PC to run it on a Mac. (I´ve noticed that you are on Mac, Bash. So am I) Since it´s a small App, it runs very well, so I haven´t tried to port the Linux version to MacOS X.
Should´nt be a problem, though.
"Play it right, Dad ! No More Dwiddely Dwiddely !
My son Adam at 3 years old. Best advice I ever got..