SOMERVILLE, MA—A fog machine heightened the drama at a children's piano recital Sunday, injecting considerable tension into an otherwise routine affair. "Right in the middle of Timmy's performance of 'Swanee River,' the smoke machine went off," said the boy's mother, Gloria Reid. "Everyone started to 'ooh' and 'aah.' I was so proud." For the next recital, organizers plan to install a giant, lava-spewing volcano.