Bala

Copperbox revision 97.

I've added an example module Korda to display pitches from guitar chord fingerings.

While it is just a sketch it did point out that the PitchRep module needed some facility to perform limited calculations on pitches (i.e. add semitones or octaves to them). Two type classes have been added to PitchRep to add and subtract semitones and octaves.