MUSIC: It's a slow night for music in Toronto, unless you're a fan of some band called "Led Zeppelin." If this is the case, you should head over to the Molson Amphitheatre, where singer Robert Plant will inevitably play mostly new songs with vocalist Alison Krauss, and Zeppelin fans will regret having paid the outlandish $40 to sit on the Amphitheatre's lawn. With T Bone Burnett. Molson Amphitheatre (909 Lakeshore Road West), 7:30 p.m. $39.50–$99.50.......