What the World Needs Now - S6-E6
Continuity mistake: When Rachel is singing the final long note of "Promises, Promises," she slowly raises her arms to above shoulder level. Then, a shot from behind shows her arms well below shoulder level, then a return to a front shot shows her arms slightly above shoulder level again.
Answer: According to IMDb.com, Ian Brennan, one of the "Glee" writers and producers, is listed as the uncredited narrator voice.
Michael Albert