By DANIEL J. WAKIN

Opera houses, ballet companies, even the National Theater in London, are competing to lure audiences to live high-definition broadcasts in movie theaters. It is the HD-ification of the arts, and it is already affecting programming decisions along with costume and set design, lighting choices and even ticket prices. Now orchestras are hoping that big screens can entice new fans to watch black-clad musicians playing instruments.

The Berlin Philharmonic, the Vienna Philharmonic and the Philadelphia Orchestra are all playing live on screen. While the HD phenomenon brings performances to millions of people who would not otherwise see them, it also raises major questions.

In a cultural world in which even the use of a microphone creates shock waves, how will the new onslaught of electronic sound change people’s expectations? The Metropolitan Opera in New York pioneered the practice five seasons ago.

This season, it is transmitting 12 operas live on Saturdays, reaching roughly 1,500 theaters in 46 countries. The Met said 2.4 million tickets were sold last season alone. The Royal Opera in London and La Scala in Milan are each offering two live opera feeds this season, and the Gran Teatre del Liceu in Barcelona is providing one.

Emerging Pictures, a distributor of European fare, is beaming eight live ballets from the Royal Ballet in London, the Paris Opera Ballet and the Bolshoi Ballet in Moscow.

The distributor has provided opera-casts from 11 other companies or festivals in the last several seasons. The National Theater’s six live transmissions will reach 330 cinemas worldwide. But the two Royal Opera live broadcasts are down from five last year, and so far few of the half-dozen Italian opera houses have signed on again this season.

At the Met, consideration is given to how sets and costumes will look on screen. Singers at such broadcasts say they are acutely aware of close-ups. Some critics have questioned whether smaller voices will gain favor. High-culture performances were common on television in past decades. Operas have long been turned into movies. The market is flooded with DVDs of recorded performances.

What is new is that the showings are live, on a big screen and part of a collective experience. “It goes back to the root of what makes live performance work, the sense of being in a space and experiencing something collectively,” David Sabel, the producer of the National Theater broadcasts, said. “You’re experiencing it in the moment, and then it’s gone.” Multiplex operators are happy to have events to show during off-hours.

They can also charge more than for the typical movie ticket. The new technology comes at a time when cultural institutions are fighting for attention. Movie broadcasts reach people who would not go to theaters for whatever reason: home competition like on-demand movies, or the inconvenience of fighting traffic, or $250 tickets, or maybe distance. For orchestras, the concept is more of a gamble.

Movie audiences have plenty to watch when costumed opera characters carry out lusty, murderous or comic doings. Ballet dancers gambol across the stage, a feast for the eye. But orchestra players tend to wear black and just sit there (although Gustavo Dudamel, the conductor of the Los Angeles Philharmonic, is a kinetic, hair-flopping presence). They also tend to play it safe when they know a film is being made that would preserve every error.

And there is nothing to make up for substandard movie theater sound systems during a symphonic concert. Deborah Borda, the president and chief executive of the Los Angeles Philharmonic, argues that the medium will work for orchestras .

“The goal is not just to promote the Los Angeles Philharmonic but to strengthen the audience for classical music around the country,” Ms. Borda said. “The audience for this, if it’s working in the way we think it can, will grow.”