   {name: 'Major 7th', abbr: 'maj7', pitch_classes: '047e'},
   {name: 'Minor 7th', abbr: 'min7', pitch_classes: '037t'},
   {name: 'Dom 7 b5', abbr: '7b5', pitch_classes: '046t'},
-  {name: 'Min 7th b5', abbr: 'm7b5', pitch_classes: '036t'},
-  {name: 'Half-diminished 7th', abbrs: ['ø', 'Ø'], pitch_classes: '036t'},
+  # following is also half-diminished 7th
+  {name: 'Min 7th b5', abbr: ['ø', 'Ø', 'm7b5'], pitch_classes: '036t'},
   {name: 'Dim Maj 7th', abbr: '°Maj7', pitch_classes: '036e'},
   {name: 'Min Maj 7th', abbrs: ['min/maj7', 'min(maj7)'], pitch_classes: '037e'},
   {name: '6th', abbrs: ['6', 'M6', 'M6', 'maj6'], pitch_classes: '0479'},


chord_book = (options) ->
  page_count = options.pages
  book "Combined Fretboard Chords", pages: options.pages, (page) ->
    for chord in Chords
      page -> chord_page chord, options

# chord_page Chords[0], best_fingering: true
# intervals_book by_root: true
# intervals_book by_root: false
chord_book best_fingering: 1, pages: 0
# chord_fingerings_page Chords[0], 44 + 3

  {barres} = options
  draw_strings()
  draw_frets()
  if barres and (pos for pos in positions when pos.fret > 0).length > 4
    fret_rows = for fn in FretNumbers
      (for sn in StringNumbers
        if _.find(positions, (pos)-> pos.string == sn and pos.fret > fn)
