It is a curious and unrelenting obsession that drives a hard-core country rockabilly music researcher like Richard Weize, head of the German reissue label Bear Family Records.

With the methodical and sometimes grating persistence of a dime-novel private eye, he will spend 15- or 16-hour days rummaging through record-company vaults, browbeating label executives or burning up the transcontinental phone lines to other scholars and collectors in his field, in search of some never-issued and long-lost recording by Lefty Frizzell, Roy Orbison or Conway Twitty. And more often than not, he will not let up until he finds it.

Weize is a man with a mission. Working through his Bremen, West Germany-based Bear Family label, he is currently in the midst of one of the most ambitious reissue programs ever undertaken in country music.

"Right now, Bear Family is the best country reissue label in the world," says Charles K. Wolfe, a professor of English at Middle Tennessee State University. Wolfe, one of the nation's foremost country and folk music historians, has often collaborated with Weize on various research projects.

"Nobody has done a better job," Wolfe adds. "And this includes similar projects by the Smithsonian, Time-Life and the Nashville-based Country Music Foundation."

"Basically I put the stuff out because I like it, and I feel someone has to do it," Weize explains as he pauses during a recent trip to Nashville, where he is immersed in scouring through hundreds of hours of indexed master tapes from the old Sun Records catalogue. This is in preparation for a 10-LP boxed set he plans to release next year of early Sun recordings. "When you get down to it, I put these things out more for myself than I do for the customer," he adds.

With more than 200 titles already in the Bear Family catalogue, he has more coming, at the rate of nearly 50 a year. He is still furiously searching the annals and archives of '50s rockabilly and country music of the 1940s, '50s and '60s, fervently repackaging and re-releasing long-overlooked and forgotten sounds (some of them gems, a few of them clunkers; some celebrated in their own day, some barely noticed and quickly forgotten).

The success of Bear Family has sparked some competition in recent years (Charly Records in Britain and Castle Records in West Germany, to name but two). But Weize has set new standards with exquisitely pressed programmed, packaged and annotated collections (often including never-released material as well as recordings long out of print) by a host of leading lights in country, as well as rockabilly, western swing and even cowboy music. Johnny Cash, Jerry Lee Lewis, Waylon Jennings, the Everly Brothers, Roy Orbison, Marty Robbins, Conway Twitty and Bob Wills are just some of them.

To his credit, he's also afforded a second hearing to the recordings of noticeably more obscure but often no less talented singers like Ferlin Husky, Tibby Edwards, the Collins Kids, Anita Carter, Lawton Williams, the Browns and others. Most of this material is obtained by leasing it from the major American labels that still hold the rights to it, but have no inclination to re-release it themselves.

Reissuers have long been mining the jazz and pop music of earlier decades but, perhaps because it has too often been looked upon as the ignorant and unwashed stepchild of other forms of popular American music, such efforts in the country field, until the past decade or so, were relatively few and far between.

At first glance, Weize, 40, seems an unusual candidate for his self-chosen ethnomusicological pursuits. A native of the Hartz Mountain region, he is six feet tall and almost gauntly thin, with a thick red beard and a matching ponytail that cascades down over a rumpled flannel shirt. He has about him a sarcastic bluntness and barely restrained sense of impatience that can easily be misinterpreted as outright truculence. When registering annoyance, his smile can quickly fade into a Teutonic glower, giving him the appearance of a Hell's Angel who just wasted five minutes trying unsuccessfully to kick-start his Harley.

But such mannerisms have not always worked against him as he has waded repeatedly through masses of misinformation, obfuscation and indifference. As Weize will tell you, he's come up against his share of Nashville record executives whose sense of musical history seldom extends past last week's top 10, and who are far too busy hyping the latest Willie Nelson-Julio Iglesias single to be bothered helping to locate or rerelease old Johnny Horton or Lefty Frizzell masters languishing in their vaults.

"The major labels are essentially marketing companies and they could care less about historical things," he says matter-of-factly. "So sometimes it is very difficult for me. I want something and I can't wait. And the more resistance I get, the hotter I get. Sometimes I have to talk to people 20 or 30 times before I get what I want. But somehow, I usually manage in the end."

Weize traces his love of American music back to his boyhood, when he first heard Fats Domino, Bill Haley and Elvis Presley on West German radio. By the time he was a teen-ager, he'd already begun the personal record collection that now numbers around 40,000 LPs and singles. ("The first country records I remember having were Marvin Rainwater's 'Two Fools in Love' on German MGM and Lonnie Donegan's version of 'The Battle of New Orleans,' " he recalls.) Later, he began contributing columns to several collector-oriented European music magazines and buying American LPs wholesale by the case from New York exporters for himself and collector friends.

In 1973, after five years spent in Britain (where, with a smattering of English, he made an uneven living working for a West German company, selling French wine to the British), he ended up back in West Germany. Still selling wine by day, he began managing, booking and occasionally recording several local German folk acts. Two years later, deeply in debt, with three children to feed, he founded Bear Family records with a $1,000 overdraft from his bank. (Some collectors note a surprising similarity between unauthorized or "bootleg" releases that appeared in West Germany around this time, and collections of American music that later found legitimate release on the Bear Family label.)

Bear Family's most ambitious project to date, and the one that has done more than any other to put Weize on the map, is "Lefty Frizzell: His Life -- His Music" (BFX 15100). Released late last year, this 15-LP, 239-song (50 of them previously unissued) set, complete with a 128-page biography and discography compiled by Weize and Charles Wolfe, is the most comprehensive package ever assembled on a single country artist.

Frizzell, who recorded from 1950 to 1974 and died in 1975 at age 47, was arguably the most influential singer in the country field since Jimmie Rodgers. Though Hank Williams, with his memorable compositions and tragic ethos, has eclipsed most other artists of his era (the late 1940s and early 1950s), it was Frizzell whose unique, dexterous singing style indelibly influenced a younger generation of soon-to-be country stars like Willie Nelson, Merle Haggard and George Jones.

"I spent three years on that and far too much money," Weize laments of the Frizzell set, which garnered rave reviews in such unlikely places as Playboy and The New York Times, and which, despite its hefty $130 price tag, sold well beyond expectations. (Weize says it sold around 1,000 units -- about average for his releases; other insiders believe it has sold considerably more.)

"It would have to sell 6,000 copies before it will pay for itself, which it might do in 30 years," he frowns. "But Lefty was one of the most important singers in country music, and I simply felt it had to be done. It was the craziest thing I ever did." He suddenly breaks into a grin. "But of course, there are even crazier things on the way!"

Some collectors wonder among themselves if there isn't a dark cloud in the silver lining of Weize's success. Now that he's compiling and releasing as many as 50 new LPs and boxed sets a year, there are questions as to whether he can live up to his own standards of excellence. After all, this is a guy who has been known to postpone a boxed-set project for months while he tracks down a single bit of historical data or a solitary photograph that he deems necessary for the set's completion. This is the fellow who once dumped 2,000 copies of a freshly pressed album in the garbage bin when a leasing contract with a major label that insisted on doing its own pressings resulted in shoddy sound quality. (Unbeknownst to the company, he repressed the album using his own money and master tapes obtained by unrevealed means.)

And even as colleagues like Wolfe take vicarious delight in his sometimes undiplomatic encounters with pompous record executives, they also concede that he may sometimes be unnecessarily burning his own bridges.

"He's big and wild looking and openly disdainful of the current country music scene," Wolfe explains with barely restrained glee. "He'll go into some label head's office wearing a dirty T-shirt and patched blue jeans, with this attitude that he knows more about the music than they do -- which he does. And somewhere along the line, when he learned colloquial English, he got the impression that when you do business, you have to use a four-letter expletive in every other sentence."

"Somehow one has to find a way to be a nut about these things and to bother people to get them done without being too much of a bothering nut," Weize explains of his aggressive negotiating style (or lack thereof). "Sometimes you walk on a very thin -- how do you say it? -- top of a hill. Sometimes you make it, sometimes you don't."

For the time being, Weize is plunging ahead undaunted. He has a whole slew of new Bear Family reissues either already in production or on the drawing board: the Sun Records boxed set ("Johnny Cash, Carl Perkins, Jerry Lee Lewis, as well as a lot of unknown stuff and some unissued stuff"), a 10-LP collection of Jerry Lee Lewis' entire output for the Smash and Mercury labels, an eight-LP reprise of Conway Twitty's early recordings, a picture disc series on Roy Rogers and other B-movie western stars, a previously-unissued album's worth of Don Gibson with Los Indios Trabajeros . . . Then there is a raft of releases on lesser-known talents like Sheb Wooley, Jimmy Work, Ed Bruce, Sanford Clark, Louis Jordan, Skeets McDonald . . . And more and more.

"I know sometimes when I first come around looking for this old stuff, many of these people are thinking, 'Look out, this guy is a nut,' " Weize says, smiling broadly as he savors the use of one of his favorite English colloquialisms. "But I think in the end most have come to feel like, 'Okay, so he's a nut, but he's a nut who makes good business. So let him be a nut! Let him do it!' And so far, no one has kicked me out of his office," he adds as he breaks into boisterous laughter. "Who knows? Maybe they will tomorrow, but not yet!"

Bob Allen, the biographer of George Jones, specializes in country music.