A sense of adventure lost. And found.

New evidence that the opera world is fickle is about as shocking as a revelation that politicians lie or that divas hate (or at least used to hate) to diet. Still, topsy-turvy is news, and topsy-turvy opera is.

Wasn’t it just yesterday that San Francisco Opera went from brain dead and irrelevant to brainy and meaningful, that Los Angeles Opera was ready to sample every wonderful new flavor under the sun (and invent a few of its own), that Chicago Lyric Opera put America first and that the Metropolitan Opera was a big, fat, plush red velvet 19th century cocoon where the rich could beam at a chandelier that goes up and down, ooh and ah over sets that looked like living rooms even they couldn’t afford, and dine elegantly in the Met restaurant no longer named for disgraced former donor Alberto Vilar?

These companies, America’s four largest, have lately announced new seasons, capped by the Met, the country’s most expensive performing arts institution, which exploded some small bombshells at a news conference in Manhattan on Monday that were apparently loud enough to be heard over the noise of snowplows. Reverse is the direction of the day. Wherever these companies were going last year they are not going next year.

For the most part, a new wave of conservatism has hit opera, as it has infected all the arts in America. This is a conservatism not of conviction but of caution. Economic prudence is probably the principal concern. Opera is obscenely expensive, and -- in the absence of significant government support -- no U.S. company is particularly flush. L.A. Opera, for instance, canceled a new work slated for this season -- the highly anticipated “Alice,” by the hot young South Korean composer Unsuk Chin -- after the company’s experimental run of the Stephen Sondheim musical “A Little Night Music” in the summer of 2004 didn’t do as well at the box office as expected and left a large deficit. The Met will come out in the black this year only because it wheedled an extra $25 million out of Mercedes Bass to make up for money it had expected from Vilar pledges that fell through.

The inclinations of big money normally are not adventurous, and the companies reflect that. But there is also a climate of fear of offending an increasingly puritanical public. Although political and moral issues are an essential part of much great opera (Mozart’s “Marriage of Figaro” all but calls for class revolution; the political message of Verdi’s “Nabucco” became a national cry for Italian unification), these are touchy, politically divided times, and few arts administrators seem willing to take chances.

Not only will there be no new operas in San Francisco, L.A. or Chicago next season, there will be nothing from the past half-century. What there will be from the 20th century includes operettas and such standard fare as “Turandot,” “Der Rosenkavalier” and “Porgy and Bess.”

Nor are companies very daring with their choices of directors. Particularly disappointing is the situation in San Francisco, where David Gockley has just replaced Pamela Rosenberg as the company’s general manager. Gone, it seems, is Rosenberg’s provocative intellectual approach of using opera as a lens for the exploration of social issues, and gone, so far, is her extraordinary attention to new and relevant work. Gockley -- who did champion new opera at Houston Grand Opera, which he headed for 33 years before beginning at San Francisco last month -- has promised a new opera from Philip Glass the season after next. But for 2006-07, he is playing it 100% safe.

Thus Monday’s news that the Met is going to try a few new things has the opera world abuzz. Peter Gelb -- formerly a record executive with a reputation for trying just about anything he thought would sell, be it the wildest of the avant-garde or the dopiest of crossover -- will officially take the reins of the Met this summer, although he’s been hanging around the company for more than a year learning the ropes. And if Gelb can manage the Met stage as well as he stage-managed his season (actually seasons) announcement Monday, with judicious leaks to the media to build up anticipation, he may be a breath of fresh air.

Many of Gelb’s ideas are long overdue. His plans to bring in directors with theater and film experience can’t hurt. But only at the Met would choosing a production of “Madame Butterfly” by the film director Anthony Minghella to open next season seem a bold move. This production, which is said to be very beautiful and was well liked at English National Opera last year, was meant to help mollify a London public usually given a heavy dose of controversial fare.

Again, asking Mark Morris to direct Gluck’s “Orfeo ed Euridice,” starring the incomparable Lorraine Hunt Lieberson, is an excellent idea, but hardly newsworthy -- Morris has done it before. Asking James Levine to stay on for the rest of his life as music director (he’s committed through 2013) is a no-brainer.

On the other hand, inviting Tony Award-winning director Mary Zimmerman to make a new production of Rossini’s magical “Armida,” with Renee Fleming in the title role, is inspired, as is teaming Esa-Pekka Salonen with the veteran French director Patrice Chereau for Janacek’s “House of the Dead,” even if Chereau was a more important force in opera 30 years ago. A “Carmen” co-directed by Matthew Bourne and Richard Eyre (responsible for the hit “Mary Poppins” in London) is good show business, especially since it is scheduled to feature Angela Gheorghiu and Roberto Alagna.

But these productions are down the line. Also some years hence, Osvaldo Golijov has promised an opera for Fleming. John Adams’ “Doctor Atomic” will find its way to the Met in 2009, which means that director Peter Sellars will then make his long-delayed Met debut. A new “Ring” cycle directed by Robert Lepage, whom the Met calls a visionary (despite his selling out to Cirque du Soleil to produce the $200-million Vegas extravaganza “Ka” last year), has been announced for next decade. At long, long last, Gelb will put some modern art in his too big, ornate, badly decorated barn.

Gelb also says that he will work with Lincoln Center Theater to develop new kinds of musical theater with serious Broadway-style composers and librettists too interesting for Broadway. That’s probably raised the most eyebrows. But it will be a sideline of the Met’s main season and, I expect, no big deal one way or the other.

For anyone to think that any of this is extraordinary only goes to show just how seriously behind the times the Met has been for the last 75 years or so. And the biggest question will be the degree of Gelb’s stick-to-itiveness. At Sony Classical, the label he headed, he tried many worthwhile things, but he had a poor record of giving them the long-range support they needed.

In all fairness, Gelb has been tricky in stealing the thunder from L.A., San Francisco and Chicago by announcing so many plans for the future. Rumor has it that L.A. has a visionary “Ring” in the works. Gockley surely must have some new ideas for San Francisco in coming seasons -- he can’t go on with endless “Carmens” and “Rigolettos.”

Chicago was a co-commissioner of “Doctor Atomic” and will mount it next season, beating the Met. L.A. is lining up new operas for every year (if not every season) and is opening its doors more than ever to Hollywood and Broadway directors.

Still, it’s been a long time (before most of us were around) since the Met has been a leader in any way. If Gelb can make even a small difference, that may help turn things around in these tame-opera times.