Bala

Copperbox revision 173.

Changed the EventTree representation from a snoc list that was counter-intuitive to traverse to a sequence with 'grammatical elements' . An explanation is probably clearest with examples:

A chord <> - this is a sequence of five elements (<) is BeginPar ('begin parallel' - chords are parallel sequences of notes, (>) is EndPar.

Similary the note c with two grace notes before it is - { e d } c. ({) is BeginPre - 'begin prefix' - grace notes are played respective to the note they precede rather than to global time, and (}) is EndPre.

Left to right traversal of this representation is much more obvious, plus because it is built on Sequence from the hierarchical libraries adding to the right end is supported.