     }
 
     /**
-     TODO: docstring
-     
-     - parameter index: The index of the note in the specified note set.
-     - parameter setIndex: The index of the note set holding the note.
+     Returns tie state of note at `index`.
+     
+     - parameter index: Note index.
+     - parameter setIndex: Note set index.
      */
     private func tieState(for index: Int, inSet setIndex: Int) throws -> Tie? {
         return try note(at: index, inSet: setIndex).tie

    }

    /**
     TODO: docstring
     */
    private mutating func recomputeNoteCollectionIndexes() {
        noteCollectionIndexes = [[NoteCollectionIndex]]()

    /**
     Returns the `NoteCollectionIndex` for the note at the specified note set and index.
     
     - parameter index: Note index.
     - parameter setIndex: Note set index.
     - throws:
        - `MeasureError.noteIndexOutOfRange`
     */
