The Sing-Off is an American show. Currently in its third season. I got it off the internet. ^^

The only a cappella performance from Arashi off the top of my head is 'Kimi Ga Iinda' from MSte. They did a minute or so of that before going into Tomadoinagara. I love Kimi ga iinda. If only they performed it again... ^^

I would love to watch The Show DVD. J-Storm, why aren't you releasing it? Yeah, another solo concert would be difficult to do these days. Arashi have a lot on their plate...