Poor Tejano conjunto. It is a doubly marginalized music. This Tex-Mex sound, driven by accordion and bajo sexto, has been mostly ignored by Anglo media and Anglo audiences, even as they down Tecates at their favorite Mexican eateries. Conjunto has also been historically shunned by middle-class Tejanos, partly because of the music's associations with excessive drinking and the baile de negocio, the taxi dance still connected with lower-class cantinas. Even among some Tejano musicians, conjunto is derided as primitive country music with a monotonous drum beat and lacking all sophistication.

This paradigm may sound familiar to blues fans. Just recall how the 12-bar form was once ignored by middle-class African-Americans who considered the genre too trashy, too lower-class.

Working-class Tejanos have always embraced conjunto as the soul of Tex-Mex culture. Now, thanks to conjunto musicians such as Flaco Jimenez and Anglo aficionados like the late Doug Sahm, this uniquely Texan music has insinuated its way into the mainstream repertory of such artists as Emmylou Harris, Dwight Yoakam and Los Lobos.

Despite the demographic shift, however, conjunto remains unknown territory to many. This Rough Guide primer should go a long way toward introducing the music considered the quintessence of Mexican border culture -- its soul, as it were. The whopping paradox here is that this introduction comes courtesy of a British-based label (though by now we should be accustomed to these odd juxtapositions with Rough Guide). With its 30-plus albums, Rough Guide has also provided us with insights into genres as diverse as Irish folk and Australian aboriginal.

The collection is a sonic road map to the great innovators of conjunto. The first was Narciso Martinez, who radically changed the genre much in the same way Clifton Chenier changed the face of Cajun music. Martinez's "Muchachos Alegres," included in this collection, features a sharp attack on the treble buttons, an approach that expanded the melodic and rhythmic shape of the sound. Another was Valerio Longoria, whose "Ramona" is included. Longoria introduced the trap drum into the basic conjunto lineup.

A third groundbreaker, Paulino Bernal, is represented by "Voy Perdiendo," recorded with his band Conjunto Bernal, an influential ensemble of the '60s and '70s. The most recent innovator, also represented on the compilation, may be the most overlooked: Flaco Jimenez, the Texas Tornado whose "Mentiste Cuando Dijiste" and "Juarez" are included, has introduced rock and pop elements to the form and served as the music's ambassador by playing with dozens of popular artists.

This 19-track album, by virtue of its star power alone, is the best introduction to conjunto on the market right now. Consider it a guidebook for Texans who don't know all the musical back roads of their own state. -- Aaron Howard