As the production moves toward its final performance, this Sunday, and the chief challenge of the week becomes the setting-up to film the show for "Live from Lincoln Center," I find myself drifting back to The Book: Act One, by Moss Hart. I've been scanning the text to see if it comments on what has taken place over the past four months, from rehearsals to previews to performances to farewells. The book does, indeed, cast a retrospective glow. Its observations about the theatre did not require an enactment to demonstrate their brilliance, but James Lapine's adaptation reminded us of their aptness. 

The translation to stage has afforded a wonderful chance to measure what has changed in the theatre and in New York since the book's timeframe, essentially the 1920s. For one thing, the sheer volume of shows then remains eye-popping. As Hart observes, "One memorable week eleven new plays all opened on the same night." For another, the period of Hart's apprentice was a time when to be in the theater was to be at the center of American show business. Radio was in its infancy, movies were still mute, and television was a notion that only futurists such as H.G. Wells could envision. 

Today, Broadway has become a place to ratify success as much as to launch it - the venue to which stars such as Denzel Washington return after making it in the movies, or celebrities such as James Franco debut in order to burnish a resume. For Hart, Hollywood was anathema even before he went there: it's no accident that Once in a Lifetime, his first big hit and the focus of act two ofAct One, pokes fun at Tinseltown and its follies. 

Not only theater's place in the wider culture has changed since the 1920s: so have the conditions under which a production comes together. There have always been theater obsessives who flock to the first preview and immediately convey to their friends exactly what they think. Hart notes that at the Brooklyn try-out of Once in a Lifetime there were plenty of "those faceless folk on the periphery of the theatre to whom it is all-important to be in the know and to know in advance just how good or how bad the incoming merchandise is likely to be." Today, such culture vultures not only swoop down on a nascent production but, through social media, tweet their impressions to, quite literally, the whole world. How directors and writers and actors withstand the scrutiny is a marvel. More than ever, toughness comes with the territory. 

All the same, I wonder if even actors as resilient as those of LCT's Act Onewould have flourished in the theater of Hart's professional infancy. In his memoir, he describes two of the performers who were veterans of the one-night-stand tours assembled by Hart's first theatrical employer, the producer Augustus Pitou, Jr. "When one considers," Hart writes, "that Fiske O'Hara invariably sang ten or twelve songs during the course of his performance each evening, and that May Robson - already nearly sixty - was duly expected, as the star of her production, never to leave the stage for more than a few moments, the conclusion that a more rugged breed of actors existed in those days is inescapable." 

If stage actors in those days were made of sterner stuff than their counterparts in 2014, I must still point out just how tirelessly the cast of LCT'sAct One has toiled. It has been a physically demanding show: running up the stairs of Beowulf Boritt's marvelous merry-go-round set (for which Boritt deservedly won a Tony last Sunday) has been a daily work-out. I wonder if even O'Hara and Robson could have withstood those rigors. 

Whatever the changes between the actors of the 1920s and those of today, at least one thing has remained constant: their need to be fearless. As I have made my rounds backstage these past four months, and observed the daily lives of the performers, I keep hearing Hart's words early in Act One: "There can be no denying the fact that offering one's physical self for inspection, exposing one's talent to the test of standing alone on a bare stage and speaking out into the void of a dark and empty auditorium, is a harsh and cruel way of pursuing one's life work." 

Yet it is a way of life that is, at best, also filled with love and passion and dedication and commitment. I have seen all of those qualities on display during the run of Act One, from actors, stagehands, stage managers, dressers. They have been a true company, with a camaraderie that, even in our endlessly chronicled age, is the possession only of those who experience it directly. 

Brendan Lemon is the American theater critic for the Financial Times and the editor of