Kurt-ain call — a show about what goes into making great theater. First, a look at Alan Jay Lerner on the centennial of his birth. The lyricist for “My Fair Lady,” “Gigi” and “Camelot” was as complicated as he was talented. Then, Jack Viertel, the theater impresario, gives Kurt a master class on all the elements of successful musical theater that audiences will recognize but may not have had a name for — like the “I want” song. Finally, Lynn Nottage’s Pulitzer-winning play “Sweat” about factory workers reeling from layoffs won over New York audiences. So how’d it go over when its New York cast toured the production in the Rust Belt?