Renee Fleming and Johan Botha in The Metropolitan Opera?s <i>Otello</i>.

Under pressure … Johan Botha and Renee Fleming play the leads in Otello.

With an hour to go before the curtain rises in the grand red-and-gold auditorium of New York's Metropolitan Opera House, a 4000-strong audience is gathering to see Verdi's Otello. Around the world, at cinemas from Vancouver to Moscow, another 250,000 congregate for a live broadcast of the opera. After the performance, the production will be beamed into still more cinemas, including those in Australia next weekend.

The Metropolitan Opera's general manager, Peter Gelb, is unruffled. ''Every day is a soap opera here,'' he says.

Gelb's chief concern is his leading man, acclaimed South African tenor Johan Botha. ''I used to joke about the fact that singers basically have three states of health,'' Gelb says. ''They're either catching a cold, recovering from a cold or actually having a cold.''

Having struggled through opening night during the ''catching'' phase, then missing the next three performances, Botha is recovering. No pressure, then, that his comeback has a vast worldwide audience.

Fortunately, the leading lady is in good health and spirits. ''I have such history with the role here,'' says Renee Fleming, who plays Desdemona, Otello's ill-fated bride. In 1994, the now celebrated American soprano was the Met's Desdemona understudy. She stepped up for a sensational debut in the same Elijah Moshinsky production now being presented.

''[That] was at the very beginning of my career, and when I opened the season with Placido [Domingo] the following year, it really put me on the map,'' she says. ''Coming back to the role, and also still feeling that it's a wonderful fit, is a joy.''

Does the fact that this performance will be seen not by thousands, but hundreds of thousands, affect her? ''There's no question that there's more pressure,'' she says. ''There's no chance of fixing something if it doesn't go well.''

Nonetheless, she is enthusiastic about live opera broadcasts, which the Met pioneered in 2006. ''I really love the fact that we suddenly have this enormous audience,'' she says. ''If we were like football players and were able to see a playback of our performance every time, we'd all be better.''

The Met's move into cinemas, she says, has helped her become more than just a ''singing head''. When operas are filmed, she takes a backstage role as a broadcast host. During the 2012-13 season, which continues through to May, Fleming will host Rigoletto, Giulio Cesare and Aida.

She welcomes the opportunity to teach the audience more about the process of making a production. ''It humanises opera,'' she says. ''It also shows just how challenging it is - 200 people work backstage to make it come to life.''

Gelb is enthusiastic about the way the broadcasts take the audiences behind the scenes. ''It's like a live reality TV show,'' he says. ''Because the set [for Otello] is quite massive, I'm having a wireless mic on the master carpenter … While the technical director explains what's happening, he'll be barking out orders and we'll see scenery flying up and down.''

While each broadcast is as carefully planned as the live productions, Gelb knows spontaneity is essential to success. ''Opera fans are not much different to sports fans in their passion and fanaticism,'' he says.

Before Otello is presented for global judgment, Gelb calmly takes his leave to sit behind the broadcast director in a truck parked on 10th Avenue. This is where the broadcast comes together, with a crew combining footage from two backstage cameras and 12 in the house.

Fleming is glad the production will be broadcast in Australia, but would like to return for an in-the-flesh performance. She last worked here in 2002. ''It's a question of finding time'', she says.

Her schedule is booked years in advance, but the chances of an Australian visit may increase once the British conductor Andrew Davis becomes the Melbourne Symphony Orchestra's chief conductor in January. He and Fleming work together at the Lyric Opera of Chicago, where he is music director and she is creative consultant. Has he dropped any hints? ''We've discussed it,'' is all she will reveal.

The Met: Live in HD series screens until May 19. See sharmillfilms.com.au.