There are many great unsolved mysteries.

A good contemporary puzzler is the recently released soundtrack for the new Coen brothers film, "O Brother, Where Art Thou?" The film, loosely based on The Odyssey and starring George Clooney and John Turturro, is currently in broad but somewhat limited release, and the soundtrack is an eclectic mixture of traditional bluegrass, gospel and post-modern revisionism, featuring Ralph Stanley, Norman Blake, John Hartford, Alison Krauss, Gillian Welch and Emmylou Harris.

On paper, this album is as doomed as Elizabeth Taylor's first marriage.

Although "O Brother" has broken the $25-million mark at the box office, making it the Coens' most successful theatrical release yet, it's not the blockbuster that drives enormous soundtrack sales.

Mainstream country radio has endeavored to nail the coffin shut by largely staying away from it, and yet "O Brother" is posting incredible sales figures, topping not only the Americana chart (as expected), but the straight Billboard country chart as well, notching a third consecutive week at number one in early March. Already certified gold just three months after its release, the soundtrack also cracked the Billboard Top 20 pop albums starting in late February.

It's amazing that any album, let alone the soundtrack to a marginally successful movie, can rack up such impressive numbers with almost no mainstream radio at all.

Although the video on CMT gave the soundtrack exposure, and a handful of country music stations have added the soundtrack in regular rotation in the wake of its success (including KCYY in San Antonio, where the "I Am a Man of Constant Sorrow" single is the number one request), most are playing it as a novelty in their morning formats.

The overwhelming majority have turned their backs to it entirely.

Quite simply, the promotion of "O Brother, Where Art Thou?" is a master stroke of marketing, timing and the always intangible luck.

The soundtrack's label, Mercury Nashville, not wanting to miss any chances with the album ahead of its release last fall, turned to one of its Universal partners to help with the promotion of "O Brother."

Rounder Records, with a long history of successfully marketing Americana and roots-oriented product and distributed by Island within the Universal family, became the linchpin of the soundtrack's promotion.

"Part of our distribution deal with Island is an agreement with Mercury Nashville to work together on some of our country crossover stuff," says Brad Paul, Rounder vice president of national promotions. "When they found they were getting the 'O Brother' soundtrack, they came to us and said, 'This is really a Rounder record, and we'd love for you to help us with the set-up and work the grassroots promotion and marketing.' We approached it like we would any roots-oriented Rounder release. We made it a priority for our radio staff on bluegrass and Americana. We worked with Mercury on suggestions for which track to put on the blugrass radio sampler Prime Cuts of Bluegrass and just helped to establish that this was a real roots music record."

With a great deal of promotion (including a collectible pre-release single in a Dapper Dan tin), but very little traditional country radio to spread the gospel, 'O Brother' had to enlist reliable but limited forms of assistance: Americana radio and good old word of mouth advertising.

"The artists on the soundtrack are unquestionably in our regular rotation in some capacity anyway," says Nancy Johnson, music director for WMLD-AM in Cumming, Ga., just outside Atlanta. "Emmylou Harris is on just one cut, but she's obviously very big. Alison Krauss is big in this format, John Hartford, Ralph Stanley, it's all there. One thing I've noticed, a lot of people who don't usually like bluegrass or old-timey or Americana music might have thought George Clooney was singing ("I Am a Man of Constant Sorrow"), and they just love that one cut. I started playing it pretty heavily as soon as I got it."

John Levinsky, program director from KRXS in the Globe/Phoenix market, concurs. "I think the first I'd heard of 'O Brother' was last September," he says. "I knew it was something that was a little unusual. I waiteduntil the movie came out before I added it to the playlist, and I'm getting good phone response to it. I don't know whether it's the movie that's propelling that or whether it's the sound of the songs. The listener response is that they like the rootsy sound of it, and it was instantaneous when we added it. Nowadays, you almost have to have shared resources for the popularity to click in. The visual nature of the video on CMT, and the awareness of the film all helps. But as far as the phenomenon of it, I think it's just that people are craving that sound."

Perhaps the most unusual aspect of country radio's response to "O Brother" is its non-responsiveness. Although the album is the number one country album, country radio is devoting little or no energy to understanding why.

Two recent major annual country radio gatherings, the Gavin conference and Country Radio Seminar, both went by without a single official discussion on the success of "O Brother."

Jon Grimson, president of Counterpoint, an independent record promotion service and a board member of the Americana Music Association, was also instrumental in marketing "O Brother" beyond the traditional Americana audience."This was a special project by any definition," says Grimson of the "O Brother" phenomenon.

"The soundtrack actually came out in December, before the movie opened. Plus with the holidays coming up, they wanted to get it in the stores. I was in the position of promoting a project that the movie hadn't opened on and really try to prepare radio for what was going to happen. We were all pretty confident that this was going to be big. I don't think anyone thought it would be a gold record as fast as it did, and given another couple of months, I think it will go platinum, which is very unusual. Mainstream country radio was not really considered part of the promotion plan anyway. Mainstream country radio wants to be a pop music format, and this is ironically too country for country. Americana and bluegrass and non-reporting country radio have been hammering on this since November. Believe it or not, they can help sell albums. Very few people want to give any credit at all to them. There is airplay. It's just not 200 major market country stations."

One factor that is easily neglected in this whole issue is the music itself, as the artists involved in the movie's music have a definable appeal that attracts CD buyers.

Certainly one of the points of interest on the soundtrack are the presences of Harris, Welch and Krauss, who portray the country version of the Sirens. Each is highly sought after by their fan bases, and the fact that they have contributed something to "O Brother" that is unavailable anywhere else has likely driven a certain percentage of sales.

The music of plays an integral role in advancing the plot, and the Coens and soundtrack producer T Bone Burnett worked together to weave the two concepts into a single tapestry. Burnett's considerable musical skills and intuition were brought to bear on the soundtrack which was always intended to be much more than a score which merely sets the tone and mood of particular scenes and the movie as a whole.

The soundtrack works seamlessly in tandem with the film's visual imagery to tell a familiar story in a completely unique fashion. Still in all, it's hard to imagine that a movie that has only filled approximately 3 million seats could inspire 15 percent of those ticket buyers to purchase the soundtrack.

Perhaps the most telling fact in this whole scenario is that Mercury Nashville and Rounder began the "O Brother" promotion last fall, well ahead of the soundtrack's release, and, as Counterpoint's Grimson noted, almost two months before the film opened in broad, but sporadic release. The most intelligent and visionary aspect of the marketing of the "O Brother" soundtrack may ultimately be that it was treated like an album rather than the companion piece to a film.

Whatever is spurring the sales of "O Brother, Where Art Thou?," it continues to generate impressive units, even fending off the Grammy rejuvenated Faith Hill, whose "Breathe" made it to number five. Billboard's Fred Bronson recently reported that "O Brother" is now one of only six soundtracks to hit the top of the country chart.

With its success almost untrackable, its appeal amazingly widespread and its exposure relatively limited, the success is a plot twist worthy of the darkly twisted Coen brothers. They couldn't have written it any better themselves.

As for the attitude of country radio in turning a deaf ear to "O Brother's" message and potential, Brad Paul from Rounder sends up a flag that all of radio should heed.

"There are some big signposts out there and it's remarkable to me that people aren't paying attention to them," says Paul. "The first was the Buena Vista Social Club. The second was Ken Burns' Jazz special, and the new one is 'O Brother.' Every one of those projects screams out that there is an audience for real music, if the audience just has an opportunity to hear it."