Sure, best musical: With the passing decades, it becomes ever more clear that Meredith Willson's 1957 romantic comedy about a two-bit thimble rigger of a con man who tries to hornswoggle the good people of River City, Iowa, is an essential American musical. From its very first song, The Music Man challenges convention, challenges its performers, even challenges its audience, obliging us to pay strict attention. The first act, especially, is probably as tightly written as any show in our time. So yes, best musical. But also best temperature, best low humidity, best moon. Best overall outdoor summer theater experience. What a delight it was to sit in Forest Park and rediscover this lovable show from the past — in a staging that at the same time brought something fresh to the mix. Kate Baldwin's Marian the Librarian was no meek soprano. She was a well-rounded character, prim and proper perhaps, who nevertheless made the conscious decision to engage in a brief fling with Harold Hill that she knew would go nowhere. Baldwin's modern Marian was but one of the components that came together in this felicitous evening. And when everything comes together in Forest Park, as it did here, you find yourself wondering why you'd ever want to see a play indoors.