Allow for a chord to be input from its name (Am, Gmaj7, E13, that
kind of stuff).
It should be a very simple thing to do a first cut of.
We'd need an inverse of ChordLabel::getString (AnalysisTypes.C),
which should be easy enough; a method that gets the mask for a
chord label (the mask is just the key under which that label is
stored in ChordLabel's static ChordMap); a method that sprinkles
the right pitches for those masks into the segment (trivial);
and a simple dialog box to tie it all together.