LIKE MOST things in Texas, the Houston Grand Opera is big, brash and in doubtful taste. You could round up cattle and play baseball in its massive foyer (probably at the same time); sculptures like the wreckage of crashed cars bent into festive shapes flank the approach; and if you're daunted by the prospect of a night of vocal culture, your anxieties are soothed by someone at a piano vamping through Sinatra's greatest hits before the show.

But appearances can be deceptive. Behind its facade of Southern glitz the HGO is actually one of the most seriously innovative opera companies in America, with a record for commissions and first performances - Tippett's New Year, John Adams's Nixon in China, Bernstein's A Quiet Place among them - that would be remarkable anywhere, let alone in a Texas oil town. And besides the commissions, HGO has an equally remarkable record for rescuing forgotten repertory - such as Virgil Thomson's Four Saints in Three Acts, which has just opened in a production by the oracular grand master of the international theatre circuit, Robert Wilson.

Needless to say, the opening of Four Saints was an Event, attended by a great meet of the world's music critics come to pay homage to one of their own (Thomson was a critic on the New York Herald Tribune in the 1940s). I was among them - drawn partly by the fact that Wilson's production is coming to the Edinburgh Festival later this year, but also by a long- standing fascination with this bizarre opera, which everyone knows about but few have ever seen.

Thomson was a formative figure in American music - overshadowed by his contemporary Aaron Copland and ageing into crusty conservatism, but a sharp, smart radical in his youth, with a wryly detached approach to creativity that made him something like a Southern Baptist William Walton. Or a Southern Baptist Poulenc. As a student in the 1920s he went off to Paris, found his muse in Erik Satie, and met Gertrude Stein, the "mama of Dada", who eventually supplied the text for Four Saints. And what a text it is: endearingly impenetrable, ritualistically surreal, and perverse from the title outwards. Because Four Saints in Three Acts is nothing of the sort: it actually features innumerable saints (virtually the whole cast, with chorus) in four acts, and reveals the heavenly company at play, in ecstasy, and otherwise declaiming mind-bending banalities as though they were the Ten Commandments. Buried in the libretto is Stein's infamous "Pigeons on the grass, alas" which only works when you say it in redneck American or very affected English.

What it all means is immaterial: Thomson never knew himself, and was content to receive Stein's text as a continuous poem, with no indication of who should sing what. Moreover he entered into the spirit of the game by setting every word, including stage directions, and inventing two external commentators (like the male and female chorus in Britten's later Rape of Lucretia) who announce the scenes and inspire a debate on whether there should or shouldn't be a fourth act. Many in the Houston audience would, I think, have voted no.

But in its day - the premiere was 1934 - Four Saints was a huge success, not merely d'estime but d'argent. It was the first opera to run on Broadway, establishing a precedent for Kurt Weill and Menotti; and judgements such as "until the heavens fall or Miss Stein makes sense there will never be anything like it" in the Herald Tribune guaranteed a healthy run. What's more, it was, and is, a glorious tease: serenely purposeless but with enough potential meaning - social critique? a parody of operatic form? - to intrigue.

It's also perfect material for Robert Wilson, who has worked on Gertrude Stein before (Dr Faustus Lights the Lights at the Edinburgh Festival) and delivers Four Saints in his familiar, glacially ambiguous, dream-like style. The saints glide about the stage in genderless crinolines; sheep float like clouds down from the flys; giraffes - yes, giraffes - look in from the wings. You learn not to ask why: this is purely formal theatre, and nobody does it better.

Virgil Thomson's music is suggestively ephemeral: the sound equivalent of a Magritte, full of familiar objets - neo-classical, neo-baroque, American vernacular - that never quite add up. It's not by any means great writing, but it's elegantly turned and easy on the ear. Alas, it doesn't allow much opportunity for the singers to shine, and their words disappear into the barn-like space of the Houston auditorium. Thomson was always concerned that the words should project, and originally insisted that the cast should be entirely black on the questionable grounds that black singers have better diction. Houston's cast is not black, but it contains fine lyric voices like Ashley Putnam and Sanford Sylvan. If, as promised, we get the same at Edinburgh, I'll have no complaints.

I wrote last week about something arrogantly called The Centenary La Boheme at the Albert Hall, as though the promoters had some kind of exclusive deal going with Puccini's ghost. In fact there are productions running this month throughout the civilised world. One of them is at Houston, and this La Boheme is infinitely better than its London rival. The director is Herbert Ross, an Academy Award-winning Hollywood man (Steel Magnolias, California Suite, The Goodbye Girl) whose cinematic panache does tend to overwhelm the stage with detail. I don't think I need to know quite so much about M Benoit's family or the streetlife of Paris. But it's done with flair, and in a way that actually manages to clarify rather than obscure the key stage business. In the Cafe Momus scene - an utter shambles at the Albert Hall - there's a lot going on, but I've never been so forcefully aware of what the central characters were up to. And there's an arresting departure from tradition in the death scene, which happens in the open air to emphasise the change of season. True, Henri Murger's novel says that Mimi dies at Christmas, but Murger also says she dies in hospital, with Rodolphe nowhere near: the book is not the opera. And there's a peculiar poignancy in having her die in sunshine, amid flowers, that Puccini might just have approved of - had he thought of it himself.

Much of the reason for the success of Boheme (allegedly the world's most performed opera) during the past hundred years is Puccini's theatrical opportunism. The piece is compact (never underestimate the appeal of short operas), comfortably distressing (Mimi's death will flood your tear ducts but won't ruin your supper), and combines the winning ingredients of youth, sex and charm. Murger's idea of Bohemianism as a "vie terrible" as well as "charmant" goes largely unobserved. But of course the ultimate attraction of Boheme is its profoundly lovable score, and the Houston conductor Vjekoslav Sutej handles it with style. As do the singers. The young, largely American, Houston cast would credit any production. And although the star name, Cecilia Gasdia, produces some oddly uncultivated sounds, she's an affecting performer and, above all, interesting. Not a common quality in Mimis.

Michael White flew to Houston with help from Continental Airlines.