For a man who quit an established recording career in order to study the fine art of making violins David Bromberg sure knows how to work a room. A veteran sideman to Dylan Ringo Starr and Jerry Jeff Walker as well as a solo performer and bandleader of more than 40 years standing the bearded and bespectacled Bromberg may have kept a low profile through the so-called MTV era. But he didn't slee…