anchor.diff:  ALTERATION: ('bb' | '#' | '##');
   MODALITY: ('Major' | 'Natural' | 'Melodic' | 'Harmonic' | 'Minor');
   CHORDNUMERAL: ('II' | 'III' | 'IV' | 'V' | 'VI' | 'VII' | 'ii' | 'iii' | 'iv' | 'v' | 'vi' | 'vii');
  -CHORDMODALITY: ('Maj' | 'Min' | 'Aug' | 'Dim') ;
  +CHORDMODALITY: ('Maj7' | 'Min7' | 'Dom7' | 'Maj' | 'Min' | 'Aug' | 'Dim' | 'HalfDim7') ;
   
   NOTELETTERS: ('C' | 'D' | 'E' | 'F' | 'G' | 'A' | 'B' | 'c' | 'd' | 'e' | 'f' | 'g' | 'a' | 'b' |
                 'Cb' | 'Db' | 'Eb' | 'Fb' | 'Gb' | 'Ab' | 'Bb' | 'cb' | 'db' | 'eb' | 'fb' | 'gb' | 'ab' | 'bb' |
                 'Cbb' | 'Dbb' | 'Ebb' | 'Fbb' | 'Gbb' | 'Abb' | 'Bbb' | 'cbb' | 'dbb' | 'ebb' | 'fbb' | 'gbb' | 'abb' | 'bbb' |
                 'C#' | 'D#' | 'E#' | 'F#' | 'G#' | 'A#' | 'B#' | 'c#' | 'd#' | 'e#' | 'f#' | 'g#' | 'a#' | 'b#' |
  -              'C##' | 'D##' | 'E##' | 'F##' | 'G##' | 'A##' | 'B##' | 'c##' | 'd##' | 'e##' | 'f##' | 'g##' | 'a##' | 'b##'
  +              'C##' | 'D##' | 'E##' | 'F##' | 'G##' | 'A##' | 'B##' | 'c##' | 'd##' | 'e##' | 'f##' | 'g##' | 'a##' | 'b##' | 'R' | 'r'
   
   );
   
  
positive.code: durationFraction returns [f]:
      numerator=INT ':'  denominator=INT {$f = ($numerator.int, $denominator.int)};
  
  tonality returns [tonal]:
      tone '-' MODALITY {$tonal = self.lc.construct_tonality($tone.t, $MODALITY.text)};
  
  chordTemplate returns [ctemplate]:
      (tone '-' CHORDMODALITY {$ctemplate = self.lc.construct_chord_template($tone.t, $CHORDMODALITY.text)})
      | CHORDNUMERAL {$ctemplate = self.lc.construct_chord_template(None, $CHORDNUMERAL.text)}
      | COMMON_DURATION_CHORD_NUMERAL_LETTERS {$ctemplate = self.lc.construct_chord_template(None, $COMMON_DURATION_CHORD_NUMERAL_LETTERS.text)}
      ;
  
  harmonicTag returns[ht]:
  
negative.code:     calculated.
  
      Example: '{ <E-Major:iv> C:5 D Eb F (1:8, 2)[C:3 D:4 E] <:v> [i@C#:3 sBb D:4 Fbb]}'
  
      Secondary chords:
        General notation for the chord:
            <NUMERAL>(ChordType)?/(NUMERAL)('-' MODALITY)
  
        e.g. <F-Minor: IIIDom7/V-Melodic>, <C-Major, V/V>
  
      NOTE: Ties are in the syntax but not supported at this time.
  */
  