David Alan Grier and Company in American Repertory Theater's production of ‘The Gershwins' Porgy and Bess.’ (Michael J. Lutch/MICHAEL J. LUTCH)

For some time, Michael Kahn has wrestled with the script of a rarely performed drama by a playwright so revered that, over his career, he was rewarded with four Pulitzer Prizes. But it’s not an interpretive issue with which Kahn is struggling as much as a practical one. At a length of more than five hours and filled with rambling soliloquies, Eugene O’Neill’s 1928 psychological study, “Strange Interlude,” is considered by many to be virtually unplayable.

So, with the permission of O’Neill’s estate, Kahn, artistic director of the Shakespeare Theatre Company, is cutting at least two-fifths of the work, in preparation to stage it in March. “I think they trust me,” Kahn says of the play’s guardians, “and I am very respectful of a play that I want to bring back to the American repertoire. I do believe that classics will live if they are reinterpreted. And that sometimes means looking at the text again.”

Contemporary tinkering with a classic drama or musical — of the sort that Kahn’s company and others in Washington and elsewhere frequently undertake — has become so common that it took the theater world by surprise last month when the practice came under what amounted to an atomic attack. The bomb was dropped by none other than America’s venerated standard-bearer of musical theater, composer-lyricist Stephen Sondheim, who lashed out at the efforts by a respected company in Cambridge, Mass. — the American Repertory Theater — to overhaul one of Sondheim’s favorite musical pieces, the 1935 “Porgy and Bess.”

Sondheim’s scathing letter to the New York Times — in response to an article describing director Diane Paulus’s vision of the production — condemned what Sondheim views as the “arrogance” of Paulus and her team, thinking they know better what an audience wants from “Porgy” than did its creators, George and Ira Gershwin and DuBose Heyward.

Sondheim was particularly incensed by the assertions of Paulus — the company’s artistic head and director of the recent, Tony Award-winning revival of “Hair” — that “Porgy’s” characters were not fleshed-out enough for a modern audience. As a result, Paulus hired Pulitzer-winning playwright Suzan-Lori Parks (“Top Dog/Underdog” ) to write new lines and reshape scenes for the production, which stars Audra McDonald, Norm Lewis and David Alan Grier.

“Putting it kindly, that’s willful ignorance,” Sondheim wrote. “These characters are as vivid as any ever created for the musical theater, as has been proved over and over in productions that may have cut some dialogue and musical passages but didn’t rewrite and distort them.”

Sondheim’s vehement reaction to a production he had not seen stemmed in part from his deep admiration for Heyward and Ira Gershwin’s lyrics, which in his new analytical memoir, “Finishing the Hat,” he lauds as some of the best ever written, for their remarkable approximation of genuine speech. But beyond the composer’s emotional reply, he illuminates a perplexing issue for an American theater starved for new masters and, as a result, obsessed with its old ones: How much license-taking is healthy, and how much of it counteracts the artistic intention of the original?

A direct product of Sondheim’s high-volume public objection was a reconsideration of a Broadway run for this “Porgy,” whose official title is “The Gershwins’ Porgy and Bess.” Some reviews, by critics who traveled to Cambridge in the wake of Sondheim’s letter, have been less than kind to Paulus’s concept, which moves the story from a realistic Catfish Row to the abstracted bowel of a slave ship. The show’s New York producers announced Wednesday that “Porgy” will begin Broadway performances at the Richard Rodgers Theatre on Dec. 17.

Still, much of the “revising” of older works goes on these days without anyone kicking up a fuss. When it comes to classical theater in particular, playgoers can be forgiven for having no idea whether what they see in a modern “adaptation” comes — for better or worse — close to the source material. The crafty playwright David Ives has made a cottage industry of the form: His version of “The Heir Apparent,” based on an 18th-century comedy by Jean-Francois Regnard, has been so thoroughly re-envisioned that the Shakespeare Theatre feels safe in labeling it a “world premiere comedy.”

Not a single eyebrow was raised last year when Signature Theatre’s artistic director, Eric Schaeffer, took a scalpel to the 1988 Abba-Tim Rice musical, “Chess.” Granted, that is a work, despite its vibrantly melodic rock score, regarded as being in pressing need of dramaturgical surgery, and Schaeffer had the blessings of the songwriters and book writer to make alterations.

A little more heat can be generated when changes are executed to cater to modern refinements in cultural sensitivities: For the 1999 revival of Irving Berlin’s 1946 musical “Annie Get Your Gun” with Bernadette Peters, a book writer was brought in to eliminate stereotyped speech patterns in a Native American character. In a slightly different vein, for his 2009 revival of his own “West Side Story,” the late director and book writer Arthur Laurents recruited Broadway actor-writer Lin Manuel Miranda to reset in Spanish some of Sondheim’s lyrics to Leonard Bernstein’s music. (Some of those lyrics were restored to English after audiences complained about comprehension problems.)

Sondheim himself has allowed manipulations both simple and eccentric to his musicals: A song with sadomasochistic overtones for Judge Turpin shows up in some productions of “Sweeney Todd” but not in others, and British director John Doyle whimsically gave the actors musical instruments to play throughout his 2005 Broadway revival of the show. But Sondheim is entitled to do whatever he pleases with the products of his imagination. It’s the controversy, it seems, over how to handle our collective stewardship of classics and especially masterpieces by artists no longer around to express their wishes that has been stirred by the American Repertory Theater production.

Clearly, tensions exist between some artistic directors — custodians of their own visions and of their audiences’ tastes — and the ghosts of some creative minds of yore. As Kahn put it, talking about his cuts to “Strange Interlude,” which won the Pulitzer in 1928: “Boy, if we were doing it with Eugene O’Neill here, we’d be having lots and lots of conversations.” He reports, too, that although his company is creating a concert series of musicals based on the plays of Shakespeare, he won’t produce a revival of one of the most famous entries in the genre, Cole Porter’s 1948 “Kiss Me, Kate,” based on “The Taming of the Shrew,” because its estate wouldn’t authorize alterations.

“Not with that book,” he says, referring to what he regards as the antique dialogue by Bella and Samuel Spewack. “That book is 50 years old.”

Paulus has articulated similar qualms about “Porgy and Bess.” In the aftermath of Sondheim’s broadsides, she has largely refrained from public comment. Before the tempest, she had spoken to reporters about wanting to provide more context for the characters’ behavior, especially for McDonald’s Bess, a junkie reviled on Catfish Row for taking up with the thuggish Crown (Phillip Boykin). “I’m sorry,” she told the Times, “but to ask an audience these days to invest three hours in a show requires your heroine be an understandable and fully rounded character.”

The notion of making Bess more palatable is rooted in a desire to expose new generations of theater-goers to a piece often staged these days in opera houses. “I think there’s validity to what we’re trying to do,” declares Jeffrey Richards, one of the show’s Broadway producers. “We want to expand the audience for ‘Porgy,’ for young audiences and new audiences.”

At present, Paulus’s intentions do not seem to be conveyed with the requisite clarity: The show very much feels like a work still trying to find its urgent rationale. Perhaps the company was so shaken by Sondheim’s scolding that by the time I saw this “Porgy” on Aug. 31, the director lost confidence and pulled back from some of her experiments. In any event, the emotional tone shifted uneasily from scene to scene. Although some minor characters had been cut and expository scenes rewritten, the departures from the text came across as rather arbitrary, and the narrative seemed scattershot.

Nevertheless, that sensuous Gershwin score, as rendered by the likes of Lewis, McDonald, Grier and Boykin, had a freshness that delivered shivers to the soul. It kindled the hope that the production’s contours might be reshaped to match the production’s energy, and that “Porgy’s” authentic passions might yet be harnessed for a rousing life after Cambridge.