IT HASN'T always been "Smooth" sailing for Rob Thomas, who performs a solo concert at DAR Constitution Hall on Sunday.

Take back in 1996 when his band, matchbox 20, released its debut the same day that Lava, the small boutique label that had signed the Orlando-based band, was folded into Atlantic, part of a corporate retrenching in the face of an industry-wide sales slump. Matchbox 20 had been signed in the feeding frenzy that followed the explosive success of grunge and so-called alternative rock, but the group's debut sold only 600 copies in its first week.

"Our manager was letting us know, this might be it on this record," Thomas recalled recently, noting that a major label honcho (whom he declined to identify) "told us to go back and rewrite the album because there were no singles on it."

Except a couple of influential alt-rock stations decided that they liked "Long Day," and a station in Birmingham gave "Push" a push without any help from Atlantic, which at that point, Thomas says, "decided to give us a chance."

Gradually sales for the band's debut, "Yourself or Someone Like You," started picking up, and then they couldn't be stopped. By decade's end, "Yourself or Someone Like You" had earned the Recording Industry Association of America's Diamond Award, marking certified U.S. sales in excess of 10 million units and adding matchbox 20's name to an elite roster of artists reaching that milestone. The album now has sold more than 14 million copies.

Its prolonged shelf life, however, posed a problem for a band trying to establish its identity and rise above the morass of pop-rockers who'd arrived in the post-grunge era. In 1999, a road-weary matchbox 20 was on break when Thomas, the band's singer and principal writer, got a call from his publisher. A rock legend was looking for songs for a comeback album. Could Thomas work on a song with another writer, Itaal Shur, who happened to live just a few New York blocks away?

He could, he did and they co-wrote "Smooth" for Carlos Santana, who was also looking for guest vocalists. Thomas envisioned George Michael on "Smooth." But Thomas's girlfriend, former Victoria's Secret model Marisol Maldonado, who happened to be the inspiration for his line "my Spanish Harlem Mona Lisa," thought he should do it. After hearing Thomas's demo, so did Santana.

It turned out well: "Smooth" closed one millennium and opened another at No. 1 on the Billboard "Hot 100" chart and won Grammys for song of the year, record of the year and best pop collaboration. Santana, who hadn't been in the Top 10 since 1970's "Black Magic Woman" and "Evil Ways," experienced a gigantic comeback, with "Supernatural" accounting for nine Grammys and selling more than 25 million copies worldwide.

The "Smooth" video became a favorite on both MTV and VH1 and kept Thomas's face on TV, much as the single kept his voice on the radio between matchbox 20 albums. It also transformed Thomas from an anonymous singer in a faceless band into a frontman and pop star: People magazine named him one of its "50 Most Beautiful People," and he married Maldonado. (Their nuptials ended up on an ABC special, "Celebrity Weddings In Style.")

Now, Thomas has embarked on a third stage with "Something to Be." Released in April, it debuted at No. 1, the first solo debut by a male artist from a rock or pop group to do that since Billboard introduced its album chart 50 years ago. It was also the first of the new CD/DVD DualDisc releases to reach No. 1.

And, no, Matchbox Twenty (the spelling changed on 2000's quadruple platinum album, "Mad Season") is not over. According to Thomas, his solo album is about opportunity, not separation or frustration.

"You can be 100 percent completely happy with everything that you do within the confines of a band, so it's not like I felt anything has ever been taken away from me. But even with all that, there's still all kinds of music that you want to be a part of, all kinds of different musicians you want to work with, all kinds of music you want to write and produce and record." It's true that Matchbox Twenty sometimes rejects Thomas's offerings, including one, "I Am an Illusion," that pops up on his solo album. But, he says, "a lot of times they're right. When the record's done and you look at the songs you picked, those are the best ones to put on, and it's good to have these guys there to censor."

He also mentions the song "Recollection Phoenix." "We worked and worked on it, did it every different way, and at the end, we were just not happy with it. Then one day I played it for Willie Nelson, and he loved it and recorded it on his record [2002's "The Great Divide," which also featured two other Thomas songs]. And then the guys were, 'Well, we could have done that!' "

Them or somebody like them: Before working on his solo album, Thomas carved out a side career writing for artists as varied as Nelson, Mick Jagger, Phil Vassar, Carl Thomas, Daryl Hall and Marc Anthony. Last year, the Songwriters Hall of Fame awarded Thomas, 33, its inaugural Starlight Award, recognizing young songwriters who have made a lasting impact in the music industry.

Certainly, Santana would second that. Thomas wrote two neo-soul songs on the "Supernatural" follow-up, "Shaman," (they were sung by Seal and Musiq) and has co-written "My Man" with OutKast's Big Boi for Santana's upcoming album, "All That I Am." (Big Boi and Mary J. Blige handle the vocals.)

"I've been so fortunate with my job and with Matchbox," Thomas says. "When I choose things, it's totally based on, wow, I really like that person, or I admire that person, or I can learn something from that person. I've never had to take a money gig -- I've turned down a lot more than I've taken. I only take things that I think are really interesting, and I'm fortunate that I'm in a position to be able to do that."

It's a long way from being a 17-year-old high school dropout looking to overcome an unstable home life growing up. Thomas's parents divorced when he was 2, and he split time between his mom's trailer park home in Florida and his grandmother's house in South Carolina. Thomas, who used to sit in front of a bedroom mirror playing string-less guitar to his mother's records, says that as turbulent as his life may have been, "there were never hurricanes when I lived" in Orlando, at least until the NSync/Backstreet Boys era. "Some sort of boy band centrifugal kind of a weather thing," offers Thomas.

Thomas first played with drummer DPaul Doucette and bassist Brian "Pookie" Yale in a local rock band, Tabitha's Secret, before hooking up with Atlanta-based songwriter-producer-A&R man Matt Serletic in 1995. Serletic was impressed with Thomas's songs and eventually helped draft guitarists Adam Gaynor (discovered at Miami's Criteria Recording Studios) and Kyle Cook (recruited from the Atlanta Institute of Music). Serletic, who three years ago was named chairman and chief executive of Virgin Records, continues to produce Matchbox Twenty and handled Thomas's solo album as well.

The success of "Something to Be," and the fact that Matchbox Twenty's last album, "More Than You Think You Are," came out three years ago, has sparked rumors that the band is finished, but Thomas has proved loyal in the past: At the height of Matchbox Twenty's success, he turned down several Rolling Stone covers because they wanted only him, not the whole band. And he did wait five years after his breakout moment with "Smooth" to make his solo debut.

For "Stripped," a new in-studio performance series available on demand from Clear Channel Radio station Web sites, Thomas is heard doing three songs from the new album (the hits "Lonely No More" and "When the Heartache Ends," as well as "I Am an Illusion") along with a new version of Matchbox Twenty's "3 A.M." and a cover of Madonna's "Borderline." He says that his solo concert Sunday won't be offering straight-on covers of his band hits either.

"I've gotten the guys in my new band to write their own parts," says Thomas, explaining that "it's for us to rework it as if it's a brand-new song, so as to not take away from the other guys in Matchbox Twenty's parts. If you're a Matchbox Twenty fan, next year you'll be able to go out and see Matchbox Twenty play those songs. If you come see me, you have a reasonable expectation to hear some of those songs because I wrote them, but I don't feel right playing the guys' parts."

ROB THOMAS -- Appearing Sunday at DAR Constitution Hall.

Rob Thomas is on a solo tour, but he says Matchbox Twenty will be back.