// The NotePath object contains, for each note, all possible playable locations on the fretboard
// we will use NotePath to build a TabEntry for which all notes can be played (ie) No two notes
// should be playable on the same string.  Also, we would like to minimize the fret distance
// between playable notes.  We need to do this because the fretboard is tuned in fourths, except
// for the fifth string which is tuned in third.  The point is that for a given midi note (pitch)
// there are overlapping locations on the fretboard where the note can be played.  This is not
// a problem with the keyboard because, theoretically, the entire keyboarded can be voiced
// at once.  The fretboard is different.  If we voice a note on the first string at the fifth
// fret, we cannot at the same time, voice a note on the first string at the fourth fret.
// Along the same lines, if we build a TabEntry that contains a voicing on the first string
// at the fifth fret, it is illegal to add another entry to the tab that voices a note on
// the first string at the sixth fret.  Allowing this would nullify the previous TabEntry.
// 
// The other objective is to handle the fret-range problem.  In building the optimal path,
// we would like to overcome the problem wherebye, for instance, a note is voiced on the
// first string at the fifth fret and, in overcoming the voicing of a competing note on the
// first string at say the fourth fret, we might arbitrarily choose to voice a note that
// cannot possibly be played by an individual because the note poses an expansive fret
// traveral.  This should be overcome by choosing a NotePath space that minimizes the
// distance requried to play the desired notes.  This alone should alleviate the problem.
//
// There is a third problem which address how many notes are voiced simultaneously.
// This problem also revolves around the mechanical differences between instruments
// used to create MIDI files, and the guitar.  For instance, the keyboard is capable
// of simultaneously voicing all 188 keys.  In other words, a chord can be build on
// the keyboard that repeats the root, third, and fifth, many times (ie) ten notes
// played sumultaneously (eleven if the pianist uses his toe).  We need to limit the
// number of simultaneous voices for the guitar to six.  We do not want to exclude
// important notes in the elimination process.  We would also like to retain key
// note pitches in order to reproduce the original sound as accurately as possible.