The big brass band that Frank Zappa briefly took on the road in 1972, just before the release of his instrumental LP The Grand Wazoo, was an army of twenty out for serious business. “Nobody sings,” Zappa wrote at the time. “Nobody dances. They just play music.” They didn’t do it often enough. This two-CD set, the whole of a previously unissued concert in Boston, combines the complex, blaring tension of Zappa’s written scores and round robins of directed improvisation, with Zappa soloing on guitar with unusual, groovin’ restraint in “The Grand Wazoo (Think It Over).” “Big Swifty,” from 1972’s Waka/Jawaka, opens with dervish woodwinds and elephant-stampede trombones, then hits and stays in high flash-your-chops gear. There is also a half-hour of the oratorio “The Adventures of Greggery Peccary” minus vocals, a plus that emphasizes the will and imagination of Zappa’s composing and the fearlessness of the hot cats under his baton.