diff --git a/src/NoteDataUtil.h b/src/NoteDataUtil.h
index 167d2955f7..3aef94ca1a 100644
--- a/src/NoteDataUtil.h
+++ b/src/NoteDataUtil.h
@@ -111,7 +111,20 @@ namespace NoteDataUtil
 	void RemoveStretch( NoteData &inout, StepsType st, int iStartIndex = 0, int iEndIndex = MAX_NOTE_ROW );
 	void RemoveAllButOneTap( NoteData &inout, int row );
 	void RemoveAllButPlayer( NoteData &inout, PlayerNumber pn );
-	enum TrackMapping { left, right, mirror, shuffle, soft_shuffle, super_shuffle, stomp, NUM_TRACK_MAPPINGS };
+	/** @brief The types of transformations available for the NoteData. */
+	enum TrackMapping
+	{
+		left, /**< The NoteData is arranged as if the player was facing to the left. */
+		right, /**< The NoteData is arranged as if the player was facing to the right. */
+		mirror, /**< The NoteData is arranged as if facing a straight mirror. */
+		backwards, /**< The NoteData is arranged as if the player was facing backwards.
+					This is NOT always the same as mirror. */
+		shuffle,
+		soft_shuffle,
+		super_shuffle,
+		stomp,
+		NUM_TRACK_MAPPINGS
+	};
 	void Turn( NoteData &inout, StepsType st, TrackMapping tt, int iStartIndex = 0, int iEndIndex = MAX_NOTE_ROW );
 	void Little( NoteData &inout, int iStartIndex = 0, int iEndIndex = MAX_NOTE_ROW );
 	void Wide( NoteData &inout, int iStartIndex = 0, int iEndIndex = MAX_NOTE_ROW );