Admit it: You watch 'So You Think You Can Dance.' If not, you should give it a shot. It's really great TV -- and not in the 'American Idol'-waiting-for-the-train-wreck great TV sense. The kids on this show really can dance and compete with entertaining spirit. Not to mention that the judges actually have something useful and even informative to say, at least if you can hear it through Mary Murphy's air-raid siren. Even if you know nothing about dance (guilty!) it may well pull you in.

Anyway, when/if you watch, you will likely see something choreographed as a tango. And you may well say, "Huh? That's a tango?" It's certainly not the Gomez and Morticia Addams tango they're doing. Sometimes it's not even the kind of thing we might have seen alongside the tango-as-art-music approach of revered composer and bandoneón master Astor Piazzolla or such popularized stage presentations as the '90s Broadway production 'Forever Tango.' And what's with some 'Dance' segments being labeled simply "tango" and others as "Argentine tango?" Isn't all tango Argentine?

Look, we know there has been a lot of different music under the tango label, especially in recent years, with the latest waves of the Nuevo Tango movement and such electronics hybrid ventures as the Gotan Project. But somehow, when we see a tango, we expect Valentino with fire in his eyes and a rose in his teeth, right?

"The misconception is that it's an obscure Argentine dance," says Donald Cohen, compiler and editor of the new book 'Tango Voices: Songs From the Soul of Buenos Aires and Beyond' -- though he might have said that this is just a misconception. There would seem to be many, which to some extent is the whole point of the book, a comprehensive guide to the evolution, cultural roots and key figures, from Carlos Gardel, still the romantic tango king more than 70 years after his 1935 plane-crash death, to the present. The story's told not just in words but also in picture and through the music itself: 26 well-chosen songs presented in sheet-music arrangements for voice and guitar and on an included CD to illustrate the accompanying essays.

Cohen himself went into the project, a follow-up to his 'Fado Português: Songs From the Soul of Portugal,' a study of a similarly passion-infused and culturally complex music form, with a lot of learning to do. Even with his mother having been from Argentina and with family still in Buenos Aires, and an extensive music background of his own (he played a couple of time with Woody Guthrie and accompanied many folk singers on guitar before becoming a a professor in history and music and an attorney), Cohen quickly realized that his knowledge was sketchy. Buenos Aires, of course, was a key destination for research trips, and there he found a variety of approaches both in music and dance that quite surprised him. It certainly didn't seem to be about the stylized presentations we've come to associate with the term.

"In Buenos Aires, I literally saw 90-year-old couples dancing, and guys 280 pounds yet still light on their feet," he says. "It doesn't have to be what we usually saw pictured in the movies in the '30s. There's ballroom tango, tango for dance floors, then different levels, all quite different and don't even look the same. Some very beautiful, some very stylized, some with tuxedos, but in Argentina often with just jeans.

"And then there's vocal tango. I heard some very old ones with guitar alone, And I went to a club in Buenos Aires and they didn't have a bandoneón. A couple of guitarists play and you can get up and sing whatever you want. I heard a couple of people at one bar and this young kid got up and sang tangos that would knock you out. But you gotta go there! You don't get that here."

Here, meaning the U.S., where it's become more and more art-music and very formalized dance. "Exactly, which is fine," he says. "But that is to the rest of tango what you would consider Ginger Rogers and Fred Astaire to be to the whole world of dance -- just one tiny part."

But it wasn't just to Buenos Aires that he headed for research. "I started going into little towns in Northern Italy, and all of them had tango schools and groups," he says. "In Rome, there are 320 tango groups. "Most people don't know how influential tango was on the rest of the world. It's big in Africa, and there's a huge Japanese audience with tango orchestras there for the last 80 years. I didn't know there is Chinese tango as well."

The book covers that global span of tango, with essays and selections on the CD unrestricted by borders. Of course there's a healthy looks and listen to the Argentine history, from the 1934 Carlos Gardel recording of 'Mi Buenos Aires Querido' ("My Beloved Buenos Aires") through the incredibly prolific Piazzolla's spare 'Vuelvo al Sur' ("I Return to the South"), from the score of the 1988 movie 'Sur.'

But there's also 'Oh, Donna Clara,' a 1930s recording by German bandleader Max Raabe, the essay recounting lyricist Fritz Lohner-Beda's anti-Nazi stance and subsequent arrest and execution in Auschwitz -- where the essay notes 'Oh, Donna Clara' was so frequently performed by the ad hoc musical ensembles that it was pretty much the death camp's de facto theme song. And there's 'Satumaa,' by the Neo Rustikale Tango-Orchester, featuring singer Sanna Pietiainen from Finland, which has become a vibrant stronghold for tango. And there are selections from Yiddish, Greek, French, Russian, Algerian and Spanish artists.

The concluding track, though, may make the strongest point. 'Jalousie' was written by Danish-born composer Jacob Thune Hansen Gade in 1925 and was debuted that year when he conducted the orchestra at the Copenhagen premiere of the silent film 'Don Q, Son of Zorro,' starring Douglas Fairbanks and introducing Mary Astor. The song, Cohen writes, became an instant sensation in Denmark, and then spread to other lands. English and Spanish versions appeared in 1931 and it has had a rich and enduring life via hundreds of artists in various contexts -- Frankie Laine, Dizzy Gillespie and Yehudi Menuhin among them, as well as use in films ranging in tone from 'Schindler's List' to 'The Full Monty.'

But the version Cohen chose? It's in Vietnamese, under the title 'Hon Ghen' in a recording by Saigon native Khan Ly. Tango, it seems, took hold in Vietnam in the first half of the 20th century thanks to the French colonials.

The international reach of tango, though, is just a returned favor, as the music itself, even in Argentina, came from a convergence of a wide array of origins.

"Of course it was the European influx and not just the Spaniards that contributed to the roots of tango along with the very heavy black presence in Argentina," he notes. "There was a pervasive African influence. And the gauchos, the Spanish creoles. Then in the 1870s and '90s the Russian immigrants brought a very heavy influence, and then Italians. So you get various kinds of European music all meshed together, and I don't think there's any way to analyze or divide it up."

What would Mary Murphy scream about that?