Move default (built-in) instrument to samples/instruments dir, and load the dir for testing/rendering. This is partly to encourage use of the plugin mechanism and partly just to test it.
Don't check for end of score in Conductor#perform_sample and Conductor#perform_chunk.
Fix spelling of 'seperation' (should be 'separation').
Replace Musicality::pitch with String#to_pitch. Add Pitch#to_s method.
Add SampleFile and Sampler class, to faciliate the production of sample files.