It's soundcheck time at the Capitol Theatre, just north of New York, and Dweezil Zappa is leading his band through the songs of his father, Frank. Dweezil, 46, has been regularly performing his dad's music for a decade, but his current tour is stranger – and more tense – than any before it. Unplugging his guitar, Dweezil looks out at the empty hall. "Sometimes people in the crowd yell things out, so I talk about it onstage," he says. "I feel like people are choosing sides." RELATED Dweezil Zappa on Fight for Family Name, 'Freak Out!' Tour Frank Zappa's son...