IT SOUNDS like a bit of mythology from rock 'n' roll's distant past, but it's happening right here in 1985. An obscure accordion player from Lake Charles, La., went into his four-track garage studio and recorded his old fashioned zydeco tune "My Toot Toot." Before he knew it, the song was a runaway hit along the Gulf Coast and was inspiring cover versions and answer songs all over the country.

Playing all the instruments himself, Rockin' Sidney performed the jingly melody on the squeezebox, scraped out the rhythm on a corrugated metal rubboard and sang, "You can have the other woman, but don't mess with my toot-toot." A corruption of the French phrase "toute-toute," it means "my everything." The song's secret, though, is the simple, bleating hook that anyone can sing along with after hearing ust half the song.

The 47-year-old Sidney Simien had had modest success with a 1962 local hit, "No Good Woman"/"You Ain't Nothin' but Fine," and the latter has been covered by Rockpile and the Fabulous Thunderbirds. But nothing prepared him for the "Toot Toot Wars." When his single was released last Christmas, it soon became an underground hit at discos and on juke boxes.

This led veteran New Orleans singer Jean Knight to cut a slick pop- soul version of the song, with synthesizers replacing the accordion and English interjections replacing the French. That version, released in February, cracked the black pop stations that Simien couldn't reach. Soon both versions were hits along the Texas-Louisiana coast. Knight negotiated with the Mississippi soul label Malaco to release her version, but then she got a better offer from Atlantic's Mirage Records, which offered her national distribution. In retaliation, Malaco released a version by Denise LaSalle that was almost exactly like Knight's.

Before long, everyone was cutting his or her own version. Fats Domino and Doug Kershaw recorded a duet version (soon recut as a Popeye's Chicken commercial); Jimmy Newman did a French Cajun version; Jay & Rodney Miller did an instrumental Cajun version.

Soon there were answer songs: Leo Thomas' "I'm Messin' With Toot-Toot" and Warren Storm's "I Caught Joe Pete Messin' With My Toot-Toot." John Fogerty traveled to Crowley, La., to record a tune with Rockin' Sidney and his band for the Showtime cable TV special "The John Fogerty All-Stars." Fogerty may yet release the song as a B-side or an album cut.

Meanwhile, Rockin' Sidney's original version was finally leased to Epic Records, which has been pushing it successfully onto the country charts. The latest word is that a forthcoming Pointer Sisters version could spread "Toot Toot" all over the world.

While there seem to be million different versions in Louisiana, these are the main versions available in Washington:

ROCKIN' SIDNEY -- "My Zydeco Shoes Got the Zydeco Blues" (Maison de Soul, MSD 1009, P.O. Drawer 10-RS, Ville Platte, La., 70586); "My Toot Toot: The Original Smash Hit" (Epic, BSE 40153). The Epic EP plucks four songs from the 12-song Maison de Soul album, which of course also includes the original hit -- still the most charming version because of its homemade simplicity. The EP doesn't include "If It's Good for the Gander," which Simien originally intended as a single. This bouncy tale of sexual equality is just begging for cover versions too, as is the dance party title to the tune. On some of the less catchy tunes, however, the threadbare nature of the production becomes too noticeable.

JEAN KNIGHT -- "My Toot Toot" (Mirage, 90282-1). When Knight warns the listener "not to mess with my toot-toot," she belts it out with an authority that should intimidate any intruder. Isaac Bolden's production, though, is rather pedestrian: a cheesy synth track and a couple of drum machines. The rest of the album features synth updates of Knight's one previous hit, "Mr. Big Stuff," plus a couple of New Orleans standards and some Bolden compositions, all of which are mere padding.

DENISE LaSALLE -- "My Tu-Tu" (Malaco, 1215). LaSalle's version is based on Knight's synth arrangement, but LaSalle's vocals are more natural and more forceful, and the synths sound fuller and brighter. The flip side, LaSalle's own "Give Me Yo' Strongest Whiskey," is the kind of bluesy southern soul that Malaco is singlehandedly keeping alive.