{ "instrument" : {
    "description" : "Keyboard, Piano, ...",
    "type" : "keyboard"
  },
  // Not used, but must be non-empty to force chords flush.
  //"tuning" : [ "A1" ],
  "chords" : [
      { "name": "NC",   "keys": [] },
      { "name": "N.C.", "keys": [] },
  ],
}