After his duet with Rihanna, Martin joined the rest of his band for “Paradise,” a single from Coldplay’s latest album, Mylo Xyloto. As expected, it was bombastic and over the top. But Coldplay’s strength is in live performance, and boy, did the group deliver. Even the jaded Grammy audience members got into it, waving multicolored light-up wristbands as if they were at an outdoor music festival. This felt like a real concert, not a one-song performance inside an auditorium.