This week, The Voice moves on to the Battle Rounds competition. This used to be the low point of the series, but it’s been massaged, over the years, to make it more of a showcase duet between contestants than a grab-the-spotlight show-off fest. So there’s reason to keep watching. Other reasons include: welcoming the guest mentors aiding the various coaches (Gwen Stefani, for example, brings along Celine Dion, and Adam Levine calls on John Legend). And checking out the outfit Stefani wears for the opening Battle Round, which I can’t quite describe, but can’t quite forget, either.