Martha Clarke made her way down the house wall at New York Theatre Workshop a few weeks ago, headed for the pool of light at the edge of the stage to tell the audience why the show was about to halt: The computer running the English surtitles for her Italian-language theater piece, “Kaos,” had frozen. But before she could stop the performance, the machine started again, the emergency passed, and Ms. Clarke retreated back into the darkness.

It was the sort of trouble that Ms. Clarke, a veteran director and choreographer, could easily have avoided if she had chosen to create the piece in English. But “Kaos”is based on the 1984 Italian film of the same name and on the stories of Luigi Pirandello that inspired the movie. Using English thus felt to Ms. Clarke like a corruption of Pirandello’s language. So surtitles, the translated text projected above the performers, naturally entered the mix.

“I’m a great fan of Italian cinema, and I love nothing more than going to a foreign culture and watching and not knowing everything,” Ms. Clarke said. She decided she wanted that sense to imbue “Kaos” as well.”I think if we had had it in good old Americanese, we would’ve lost this feeling of another world and another time.”

Like subtitles for foreign-language films, surtitles for foreign-language theater and opera can open them to new audiences — but only when they’re executed well. Otherwise, they can be a source of frustration, an impenetrable barrier that inadvertently leaves the audience feeling excluded from the performance.

“What I’ve learned is that you can’t underestimate the value of a good surtitle,” said the edgy young German director, Thomas Ostermeier, who recently brought his German-language adaptation of Ibsen’s”Hedda Gabler”to Brooklyn Academy of Music’s Next Wave Festival.

Mr. Ostermeier’s company, the Schaubühne, frequently tours its productions, and customarily reworks its surtitles, as it did this fall after taking “Hedda” to Ireland. In Dublin, company members spoke with Americans who saw the production there, and used their feedback to adapt the titles for BAM.

“Showing a show abroad is not just showing what you did at home. It is something completely different,” Mr. Ostermeier said. “As an artist or director, you tend to believe that your work is so powerful that it doesn’t need explanation or translation. Which is not the case, I’d say.”

While widely accepted now, surtitles have been used in this country only since 1983, when Beverly Sills borrowed the idea from Toronto’s Canadian Opera and introduced it with New York City Opera’s production of Massenet’s “Cendrillon.”

“There was much groaning and gnashing of teeth among purists who said,’This is the end of civilization as we know it, and now the great unwashed will come storming into the opera houses,'” City Opera’s dramaturg and director of supertitles, Cori Ellison, said. “Which, of course, is exactly what City Opera is about. Fiorello LaGuardia founded City Opera as the people’s opera, and we want the people — all of them — here.”

Chief among the groaners and gnashers was Metropolitan Opera Music Director James Levine, who in 1985 famously told the New York Times, “Over my dead body will they show those things at this house.” His reasoning was simple. “I cannot imagine not wanting the audience riveted on the performers at every moment,” he said.

Within a decade, though, titles were indeed being used at the Met, with Mr. Levine alive, well, and still at the helm. The Met, however, does not project surtitles above the stage but instead offers illuminated titles on the back of each seat, giving patrons the option to turn them on or off as they wish.

“The Met has the best system,” said BAM Executive Producer Joseph V. Melillo, whose patrons-in-the-know sit in the mezzanine at the opera house and in the back of the orchestra at the smaller Harvey Theater to get the best view of the standard surtitle screens below the proscenium. Those who sit too close, or too far off to the side, must crane their necks to read the translation. Sometimes, they leave in exhausted frustration.

“Hedda Gabler” was an exception to the rule. The Schaubühne designed its own screens specifically for the Harvey. One sat on the stage and another hung above it, giving all seats a comfortable view of the titles.

For “Kaos,” New York Theatre Workshop — which has neither a deep house nor a tall one — posed an architectural challenge: Where to project the text? Earlier this season, the Spanish-language “¡El Conquistador!” projected surtitles onto the frame of its tightly contained set. In “Kaos,” the titles appear upstage right, which means they are sometimes separated by a considerable distance from the stage action.

“It was a choice about how the theater was built,” Ms. Clarke said.

Ms. Clarke, who had worked with surtitles as an opera director but had never before created them from scratch, discovered their various virtues and hazards as “Kaos” evolved. “Clarity and brevity are next to godliness,” she said of the surtitles’ content.

The text of each title must be “digestible,” said Ms. Ellison, who writes surtitles not only for City Opera but also for the Met. “And that doesn’t mean dumbing it down. It just means that your eye can take it in and your brain can process it without stumbling.”

Just as crucial as the wording of the text is its timing, which must be in sync with the performance. If the titles are mistimed — if, for example, punch lines are given away in translation before they’re spoken or sung on the stage — they can ruin a performance.

BAM started using surtitles selectively in the 1980s and with increasing frequency in 1999, when Mr. Melillo, new to his position, focused BAM’s mission on global theater. These days at BAM, particularly at the Next Wave Festival, audiences expect to see foreign-language works, but the success of each production’s translation is something of a wild card. The tone and content of surtitles are aesthetic decisions made by the director.

Forgoing surtitles altogether is director David Chambers, whose “Don Juan in Prague” just ended the Next Wave Festival on Saturday. Mr. Chambers’s adaptation of Mozart’s “Don Giovanni” is sung in Italian but spoken in English. The condensed English text, which he wrote to replace the recitatives, allows the audience understand the plot without distracting from the music or the staging.

Mr. Chambers objects to interrupting the audience’s field of vision with written text and insists that it is unnecessary.

“Language is only one component of the theater,” said Mr. Chambers, who sees a great deal of theater in other countries and has developed what he called “a kind of way of reading what’s going on” without any translation. To him, surtitled performance “becomes much more a cerebral than a visceral experience.”

But where Mr. Chambers senses containment, Ms. Clarke smells liberation. She would like to take her “Kaos” company abroad, and surtitles, which could be translated into any number of languages, provide the means to transcend cultural barriers.

“If we do well, which hopefully we will,” she said, “we could travel anywhere with it.”