...and very flexible, allows you to create not only new tunings but also new instruments as complex as Pedal Steel Guitar.
Still need some work to make it more mac friendly, and improvements to manage the amazingly rich an complex printing features. I have used this program for years on wintel, then OS9 and early on OSX and got 1rst class support from the author for any problem I've encountered.
I have tried all the tabbing programs available, not one comes even close