A `Country' Artist Who Defies Labels. Singer/songwriter Lyle Lovett reaches for a brass-and-strings section as readily as a twanging guitar, offering personal folklike lyrics in a voice of pure blues

THIRTY minutes before show time at Boston's Berklee Performance Center, some ticket-holders are talking over dinner about singer Lyle Lovett and his Large Band. ``A friend in Denver sent us a tape. And on it was an unheard-of guy - at least, unheard of by us - named Lyle Lovett. [We] flipped. We just thought it was the greatest stuff.''

Five minutes to go. The house lights flash inside the 1,200-seat auditorium, bringing stragglers in for the sold-out show. An audience member from Maine says he waited in minus-10-degree weather for 45 minutes to get his third-row seats.

``We're big fans of Lyle,'' he says. ``I bought one of his albums. ... `He's tremendous!'''

Such praise means Lyle - as everyone calls the Grammy-nominated singer/songwriter - is gaining ground in his effort to redefine music-industry categories. Nominally a ``country'' artist, the Houston native is just as likely to reach for a brass-and-strings section as a twanging guitar. His lyrics are personal and folklike, his voice pure blues.

``They've never tried to make me into the next big country singer,'' Lyle says of MCA, his record label, in an interview before the show. But he also says he was fortunate to take his demo tapes to Nashville when record companies were experimenting with new sounds.

The music industry may pay lip service to originality, but the truth is that record companies breathe easier with songwriters who will put a fresh coat of paint on a reliable old formula and drive it to the top of the charts. Traditional acts still sell the most records.

``I think it would be tougher for me to get signed right now in Nashville than it was four years ago,'' Lyle points out.

He hasn't exactly let the industry down, though. He's given country radio five Top-20 singles and one song, ``Farther Down the Line,'' in the Top 10. Still, many radio stations prefer a square peg for their square-format hole.

Yet as the Berklee house lights finally dim, the music the crowd is primed for is anything but square. The show is actually a double-headliner concert, with acoustic guitar legend Leo Kottke taking the stage first.

The pairing works well. Kottke's one-man act contrasts with Lyle's packed stage. The appeal of a veteran of 20-odd albums and years of touring complements the surging interest in the talented newcomer. Kottke dazzles the house with intricate, mostly instrumental melodies with names like ``I Yell At Traffic.'' OPENING the second half of the show, the Large Band assembled by Lyle for his traveling show appears: three saxophones, a cello, a black female vocalist, keyboards, bass, drums, and lead guitar. It stretches and struts with Clifford Brown's ``The Blues Walk.'' Then Lyle appears and works through ``Here I Am,'' a talk/song m'elange.

His famous froth of hair boils over onto the mike as he looks the audience in the eye and asks, ``Can you doubt we were made for each other?''

The Berklee audience enthusiastically receives each song, from the high-speed, country-styled ``L.A. County'' to the jazzy ``Cryin' Shame'' and ``Simple Song,'' the latter a haunting duet with cellist John Hagen. The fans also enjoy the humor Lyle delivers in between numbers.

``I don't get a lot of hate mail,'' he says by way of introducing ``If I Had A Boat.'' A letter writer has sounded off because the song makes light of the Lone Ranger and Tonto. Lyle deadpans defensively, ``I just want to say that I'm proud of everything they've ever done.''

A catch-all description of Lyle's songs eludes sax player Harvey Thompson, the foremost of the studio-caliber musicians in the Large Band. And Thompson's own Muscle Shoals Horns group has recorded with artists of every genre, more than 400 in all.

``I don't know what to call it,'' Thompson says of Lyle's music in an interview after the concert. ``It's all over the place - rhythm and blues, jazz, country.''

Lyle himself talks of writing blues songs and wanting to perform them ``in this swing, sort of pseudo big-band style.'' His lyrics are often sparked by experiences, and he extrapolates from there. The result can be hilarious, as in ``The preacher said/ `I pronounce you 99 to life/ Son, she's no lady/ She's your wife.'''

``I really have a terrible imagination, but I consider myself a very good liar,'' the never-married artist jokes.

When it comes to riveting vocals, Lyle is the equal of virtually any black bluesman who ever moaned into a microphone - not a bad achievement for a 31-year-old white boy. ``Pure excitement'' is how Francine Reed describes his chameleon vocals. Ms. Reed should know. She provides the Large Band's vocal backups and took over the stage at this concert for a show-stopping number, ``Wild Women Don't Get the Blues.''

Lyle's vocals, lyrics, and arrangements grow out of a unique artistic vision - sophisticated, smoldering, subversive. And he is determined to present that vision to his public the way it comes to him. For instance, he pestered MCA until it agreed to include the lyrics with cassette and CD copies of his third album, ``Lyle Lovett and his Large Band.''

One proof of his commitment to his listeners is that Lyle takes the band on the road. Including behind-the-scenes support, the group comes to 20 members, and that's costly, but it gives the public the sound it knows from his recordings.

With the expense of the band, Lyle might be expected to employ it throughout the show. No way. ``I still approach things from a songwriter standpoint, and try to do for each song what seems to work best,'' he says. When less is more, unneeded band members slip offstage. THE tour also tests MCA's commitment to Lyle, which he says has been strong. The road-show's head count indicates that the tour budget will dip into the red. The label is making up the difference in hopes of boosting album sales.

But Lyle and MCA find the news on that front encouraging. The 1986 debut LP, ``Lyle Lovett,'' sold 50,000 copies. The second, ``Pontiac,'' touched the 200,000 mark after it was issued in 1988. It also earned Lyle a Grammy nomination as best male country vocalist, while the cut ``She's No Lady,'' was nominated for best country song. The third album, issued just this past January, has already sold 200,000 copies.

After a standing ovation, the house lights come up and the audience heads for the exits. Backstage, sax men Andy Laster and Steve Marsh break into a countdown cheer: ``Northampton! Philadelphia! New York!''

The past month-and-a-half has taken Lyle and his group from Florida to Canada. Three more shows, and they earn an 18-day break. Lyle will tape an HBO special with comedian Steven Wright in New York, then fly to Los Angeles for a ``Tonight Show'' appearance. The band will re-form in Denver, when the tour turns west during April.

As recently as 1984, Lyle's circuit was a half-dozen clubs in Texas. That drive of his to redefine music industry conventions has taken Lyle a long way, and it's not over yet.