Re-jig note translation to only happen when we are going to emit a note. This fixes "note_off with no note_on" cases (iWriteMusic likes to emit these for rests). This means some messages have untransposed notes but we draw the line because they only have to be transposed because of limitations in the organ so before that they are are untransposed (except for the bulk adjustment)

# Introduction
This program converts a MIDI file into a series of PDF files suitable
to feed a laser cutter to cut sheets of music for a reed organ.

# Libraries Used
PDF writer - http://www.reportlab.com/opensource/
MIDI parser - https://pypi.python.org/pypi/mido