Treemonisha, Scott Joplin's most ambitious work, though not his first or only opera, is being performed in the town where he wrote it. The Opera Theater of St. Louis is performing it in the black dialect that Joplin originally intended. Joplin himself never saw the work performed - the first professional production wasn't staged until 1975, when it was mounted by Houston Grand Opera. But in the Houston performance, producers worried that the dialect would offend audiences, so "deese," "dem," and "dose" became "these," "them," and "those." Jim Dryden reports.