Despite three albums and one Grammy to its credit, one of the biggest buzz bands at this year's South by Southwest Music Festival isn't a band at all.

Los Super Seven is more like . . . a Petri dish, cultivated according to the theme of the moment.

So there's no group to reunite, no tour to kick off. Just some guys who sang on the third and latest LS7 album, "Heard It on the X," getting together with the accompanying band, Calexico, to do a few gigs in celebration of its Tuesday release.

One is at Stubb's on Saturday; another is before an invited crowd of Grammy voters; and a third is for 100 or so influential media types crammed onto the tiny back patio of Las Manitas restaurant on Congress Avenue for something called "Sunset on the Border."

That's where Los Super Seven was incubated in 1997, as a one-off SXSW showcase for Austin-bred Rick Trevino, arranged by his manager, Dan Goodman. Trevino performed with Joe Ely, Flaco Jimenez, Doug Sahm, Augie Meyers and Rosie Flores, accompanied by a mariachi band.

It sounded so good, Goodman started envisioning an album. Trevino, Ely, Jimenez, Sahm, Ruben Ramos, Freddy Fender and Los Lobos members Cesar Rosas and David Hidalgo wound up on it. Los Lobos' Louis Perez came up with the name.

After the nongroup picked up a 1998 Grammy for Best Mexican-American Music Performance, Goodman followed it up with "Canto," an exploration of "pan-Latin" music from much farther south of the border. Meanwhile, those "Sunset" Super Seven gigs continued for the next few years.

A couple of years ago, the concept returned when Goodman, with friend and co-producer Rick Clark, explored the idea of a Texas roadhouse disc. Then they hit upon the border radio theme, chose songs evocative of its late '50s-early '60s heyday, hired Austinite Charlie Sexton to co-produce, and gathered seven — make that 10 — vocalists, most of them influenced by the rock and R&B beamed from powerful X-lettered stations placed just over the United States border in Mexico — free from Federal Communications Commission regulations.

"It was supposed to be much more of a Texas record, like the first one was. Border, anyway," Goodman confesses, but the lure of "Mexican radio" pulled them in. This time, Ramos, Trevino, Ely and Fender were joined by Raul Malo (who sang on "Canto"), Delbert McClinton, Rodney Crowell, John Hiatt, Lyle Lovett and Clarence "Gatemouth" Brown.

Sexton saw to it that the original Las Manitas/"border" thread remained woven into the album via what he likes to call "breadcrumbs" leading back to "the roots of an artist or of the project."

He also strived for, in his words, "a certain 'it's in the water' aspect."

For instance, the keyboardist who performed on the original Sunny and the Sunliners' version of "Talk to Me," one of two contributions by roadhouse master McClinton, plays on the "X" rendition.

Sexton also felt strongly about infusing the album with the spirit of Sahm, who sang on a "Los Super Seven" track. The late Sahm's "X" contributions are his compositions "I'm Not that Kat (Anymore)," sung by Hiatt, and "The Song of Everything," sung by Malo. According to Sexton, Sahm's career embodied Tex-Mex and the crazy-quilt pattern of those megawatt stations where, according to Ely, "Brother Al would preach for an hour and then at the end of his show, he'd sell autographed pictures of Jesus."

That was just before the howl that signaled rock jock Wolfman Jack's show. Ely was one of a generation of kids who discovered rock 'n' roll by snatching the Wolfman's broadcasts out of the clear night air.

"We'd go out in the middle of a cotton field and somebody'd have a six pack and we'd turn on that station (XERF) and listen to it all night," remembers the Lubbock native. "That was our entertainment. . . . It was like this weird little treasure." XERF was where he first heard his "X" contribution, Bobby Fuller's "Let Her Dance."

Ramos, who sings the ZZ Top-penned title cut, remembers battling his older-brother bandmates for knob control when they refused to play the X during long drives from gig to gig. He and his younger siblings wanted to hear that sexy stuff they couldn't get on stateside stations. When their big brothers fell asleep, they tuned in to the X — which could reach them even in Midwestern states.

If border radio were still around, listeners would undoubtedly hear songs from this album, of which McClinton says, "Every cut on there is just amazing." Today, the tunes are pingponging through the air via stateside terrestrial and satellite radio signals — KGSR-FM is all over it — and via live performances at places such as Las Manitas, where the "Sunset on the Border" tradition continues with Los Super, uh, Several? And with luck, several more to come.