SEVEN YEARS ago, the threads in Emmylou Harris' cowgirl suit were beginning to fray around the edges.

The costume had once belonged to Gail Davis, television's Annie Oakley, and it was one of Harris' most precious possessions. She would wear it as she walked through the Washington nights from her dilapidated apartment on 18th Street to gigs at the Chancery, Childe Harold and Red Fox.

In those days -- except to her small but loyal following -- she was "Emmy Who."

These days her road crew has taken to wearing bright red T-shirts with the logo "Grammylou 1980" -- celebrating her Grammy for last year's "Blue Kentucky Girl" album, voted the best in country mussic by a female. Her newest album, "Roses in the Snow," is No. 2 on the country charts and No. 28 (and moving up) in the pop charts.

Tomorrow night, Harris returns to Washington for a concert at Wolf Trap.

Since 1975, she has lived in Studio City outside Los Angeles with her producer-husband Brian Ahern and three children. But this is still her favorite place: "I really don't feel like I ever got much done until I got to Washington."

She has done plenty since, and her confidence reflects it. At 31, Harris can laugh about the recent reissue of a 10-year-old pop-folk album she thought had been buried: "My road manager came up to me the other day," she says. "He said, 'The good news is -- your record went gold. The bad news is it's the bootleg album.'"

The laughter is part of her new personality. "I feel like I'm more sure of myself," she explains. "I'm not sure if it's success.' Perhaps a lot of it has come from the day-to-day thing of continuing to make music, being more experienced, knowing a little bit more about what I'm doing in the studio.

"For instance, I don't go for perfection any more. I go for 'the moment' that you get on tape. I don't try to put something onto a record that isn't already there as far as the feel of it. There have been changes." Two More Bottles of Wine

One is her growing courage as a performer. It was unveiled on last year's "Blue Kentucky Girl," which was hardcore country -- a harsh contrast to Harris' previous mixed-bag albums that ranged from country to pop to electric folk. There were worries about how her fans would react, but the record went to the top of the country charts. There were even more worries three months ago, when she released "Roses in the Snow" -- an all-acoustic bluegrass album.

"It was something I knew I wanted to do," Harris says. "It just happened a little sooner than I thought. After it was done, all of sudden I started to smell a bit of resistance from the record company: 'This is a terrible time to put out an album like that,' they said. 'The market is really down. It'll be a disaster.' I even thought about including a few broader-based songs, but Brian [Ahern] quickly shot that idea down."

Bluegrass albums have traditionally done poorly in the marketplace. With the exception of flukes like "Dueling Banjos" and "Foggy Mountain Breakdown," bluegrass gets extremely limited airplay and distribution. But, she says, "It got to feel like it was my baby and it had to come out. I'm amazed at how well it's done." So well, in fact, that Harris feels she has to reassure her fans that she is not abandoning country music.

She recorded "Roses" while she was pregnant with daughter Megan, now six months old. During the same time, she also did a major tour and recorded a second, acoustic Christmas album drawn from gospel and traditional folk sources and featuring the same cast -- Linda Ronstadt, Willie Nelson, Dolly Parton, the White Sisters -- as "Roses." "Light of the Stable" will be released this December (it was available this year as an English import).

Harris' family also includes Shannon, 12, from Ahern's first mirriage, and Harris' daughter Hallie, 10. "Our personal lives are organized," Harris says, "so that a day-to-day routine continues when I'm not there. [She'll tour for 10 days, then come home for three weeks.] It's still hard to be away. It's a balancing act to get satisfaction from both family and work. Your family does fine, but you realize you have to be there to partake of what they have to give to you."

Things weren't always so settled. Born in Birmingham, Ala., to the family of a mobile Marine Corps career office, Harris spent most of her growing years in Woodbridge, Va., where she was crowned Miss Woodbridge and was valedictorian of her high school class. At 16, she wrote to Pete Seeger, the grand old man of American folk music. "He was really my idol and I wrote him an incredible 10-page letter, handprinted front and back, about my aspiration to be a singer. He wrote me to hang in there and said he was very surprised at my letter because it was so sincere." That advice was never wasted.

A year at the University of North Carolina on a drama scholarship ended with Harris dropping out; in 1969, she moved to New York and cut a tiny swath as a folk singer in a city full of them. (Today she still remains close to some, including Jerry Jeff Walker and David Bromberg.) By 1970 she had married, had a daughter (Hallie, now 10) and cut an album called "Gliding Bird" for the Jubilee label. Two months later, Jubilee went bankrupt -- at which time, Harris' lawyers now claim, the rights reverted back to the performer. That is a major point in their current lawsuit to prevent further manufacturing of the album. A sojourn in Nashville ended with a divorce and an uncomfortable look at the bottom of the barrel: Harris was surviving on foodstamps while working as a waitress at a Polynesian restauant, "eating fortune cookies because they charged you for your meals." She though about giving up music. There was never time to practice, "spare time just couldn't be spared."

She ended up moving back to her parents. Once in the Washington area again, things seemed to break right for once. Gigs were still hard to come by, and Harris often worked for as little as $10 a night. Then, as now, she was an interpreter ("I'm just not that hung up on being a writer"), working with country, bluegrass and folk material, finding songs like Shel Silverstein's "Queen of the Silver Dollar" and Dolly Parton's "Coat of many Colors," gracing them with a classic country soprano of exquisite range and making them very much her own.

Harris booked herself into the Georgetown-Capitol Hill-Bethesda club circuit. In late 1971, she arranged a job at Clyde's in Georgetown. "They did much better business with the omeletes," she says. One night, two members of the Flying Burrito Brothers walked into Clyde's after they'd finished playing at the Cellar Door up the street. They asked her to keep singing. Harris had just finished her set, wasn't in a good mood, and didn't feel like doing any more. One can only wonder what might have happened if she hadn't.

But she finally did an encore of "It Was God Who Made Honky Tonk Angels" and fired the Burritos up. They came back the next night with leader Chris Hillman, who asked her to join the band on the spot. The next day, before Harris could reply, the band had decided to break up. The Darkest Hour

They reformed several months later under Gram Parsons, the father of country rock who always favored country over rock. He and Harris found an instant communion, though it would be a year before he could arrange for her to join him at his Los Angeles studio for the "GP" album. Their duet singing was stunning, even more so on "Return of the Grievous Angel," the album that followed.In 1973 Parsons died of a heart attack at 26. "Grievous Angel" was released posthumously -- but without Harris' name on the cover, after a threatened lawsuit from Parsons' estranged widow, Gretchen, who had been less than happy with either the musical or romatic developments between Parsons and Harris.

Harris returned to Washington, emotionally shattered but musically confident. Parsons provided two lasting gifts: He solidified Harris' stance as a country singer and "he forced me to learn how to sing, how to phrase, how to control my volume." That combination broke the cycle of rejection and failure that had surrounded her career. She put a band together and worked the club circuit. Within a year, the record companies were bidding for her. When she finally signed, it was for a reported quarter of a million dollars.

Her first Warner Brothers album, "Pieces of the Sky," was issued in early 1975 and promptly delivered an unespected bonanza: Her interpretaion of the Louvin Brothers' "If I Could Only Win Your Love." "Country audiences accepted me right from the start," says Harris -- so much so that both the single and the album became No. 1 country records, the first of many. b

In 1975, when "Pieces of the Sky" had been finished for $80,000 ("about eight times over budget") Harris said "I made my peace with money a long time ago. We did go over budget, but we did get into the next album with some tracks that are real contenders."

Three singles from the follow-up album, "Elite Hotel," also went to No. 1 -- "Together Again," "One of these Days" and "Sweet Dreams." She has produced four more albums, a "best-of" collection and more chart-toppers like "To Daddy" and "Beneath Still Waters." Harris has also developed into a trooper on the road, splitting lengthy American tours with frequent appearances in Europe.

And along the way -- like Willie Nelson and Waylon Jennings and the more traditional voices in the genre -- Harris has helped country music replace pop as the second most popular style in America after rock, according to Billboard magazine. Together Again

On radio or records, it's sometimes hard to find Harris' crystalline voice by itself. She is possibly the finest harmony singer in America, having recorded duets with (and at the request of) Bob Dylan, Neil Youg, George Jones, Linda Rondstadt, Willie Nelson, Dolly Parton, Tanya Tucker and a host of less known vocalists.

For almost two years now, fans have heard about plans for an album by what became known as the "Queenston Trio" -- Harris, Ronstadt and Parton. It never got beyond the preliminary stage (though it did produce "Even Cowgirls Get the Blues" from "Blue Kentucky Girl" and the title cut of the Christmas album). The celebrated trio remain close friends.

Harris' relationship with Ronstadt predates either of their successes. "The first time I met her," says Harris, "we were on the road in Houston. Linda was on the road with Neil Young and I was with Gram and they would come over after their concert and we just hit it off right away. She was wonderful to me, not just plugging me on stage (long before she recorded her first album, Ronstadt used to deliver a five-minute rap on Harris to her audiences) but hyping me to record people." Harris now returns the favor for songwriters like Suzanna and Guy Clark, Rodney Crowell and others who provide her distinctive material.

"It started with Gram," Harris says of the harmonizing and duet stylings. "I was so happy doing that -- the excitement of voices blending, yet something there being a little bit out of control because you have the option of going to all the notes rather than sticking to really strict parts. It's like two people singing different melodies on the same song -- different yet sounding better together than by themselves."

"Some (voices) you blend with naturally. Gram and I never had to worry or even think about phrasing. Willie's (Nelson's) phrasing is totally foreign to me, yet I love our voices together. With Roy Orbison (whom she sings with on the soundtrack to "Roadie") -- well, I never in a million years would have thought our voices would have blended. I do have a bit of a chameleon-like quality when I sing with people. I try to follow them, pick up on their idiosyncracies and try to blend with them. It's what I enjoy."

One of Harris' favorite pastimes is to sit around informally and sing: "It's where you get your blood pumping and your creative juices flowing."

After tomorrow night's concert, Harris heads for a tour of Ireland and Belgium. Seven years ago, Annapolis seemed far away. She's miles and years away from hazy spotlights and cramped stages of Washington, and probably much farther in her evolution as a person.

"I've never thought about it," she says of the distance between Emmy Who and Grammylou. "It's like two different people. But it also seems natural because it happened one day at a time."