code: function (alteration) {
          if (/sus/.test(alteration)) {
              return 'susX';
          }
          if (/add/.test(alteration)) {
              return 'addX';
          }
          if (/no/.test(alteration)) {
              return 'noX';
          }
          if (/alt/.test(alteration)) {
              return 'alt';
          }
          return 'binary';
      }
docs: /* might want this later
  var intervalType = function(parsed_interval) {
  if (parsed_interval.quality === 'P' || parsed_interval.quality === 'M') {
  return 'natural';
  } else {
  return 'altered';
  }
  };