If that guy on stage at Dino's Lounge in Las Vegas singing karaoke sounded a bit better than the average drunk piker from Minnesota, it's because he did. Coldplay singer Chris Martin took a break from his band's Music of the Spheres global juggernaut tour to have some fun in Sin City this weekend when he went incognito as a schlumpy business man on a bender while filming the video for the group's next Moon Music single,