code: function map (fn, ctx, obj) {
    switch (arguments.length) {
      case 0: return map
      case 1: return transform(fn, buildSeq, buildSim)
      case 2: return function (obj) { return map(fn)(ctx, obj) }
      case 3: return map(fn)(ctx, obj)
    }
  }
docs: Map the notes of a musical structure using a function
  
  @param {Function} fn - the function used to map the notes
  @param {Object} ctx - a context object passed to the function
  @param {Score} score - the score to transform
  @return {Score} the transformed score