Change performer to only handle a single instrument, and no effects. In score, parts are now contained in a hash and mapped by ID. Another change that is still needed is to map part ID to instument and effects somewhere in the score.
Move responsibility of producing initial (intermediate) instruction sequences into IntermediateSequencer class.
Have a different class for each kind of instruction, instead of a symbol constant and a single class to represent them all.
Combine note sequences where they are contiguous.
Add rake directive 'make_samples' that executes all make*.rb files anywhere under the samples directory tree.
Move score preparation responsibilities of Arranger into Conductor.
Change Arranger to InstrumentFinder, since that's all it does now. Make it a utility class.