Good news: There's a video that demonstrates what the gameplay for Guitar Hero: On Tour is going to be like on the Nintendo DS. Bad news: The video is painful to watch. Like, cringe inducing to the point that you may break your neck as your head tries to bury itself into your body.
We don't know if this video was even officially released; as of this writing, the versions on both GameVideos and GameTrailers were user submitted. We checked with contacts at both sites but, to the best of our knowledge, Activision didn't send this out in any official capacity (after watching, it's pretty easy to guess why).