They are free. As artists, John Linnell and John Flansburgh, the quirky alternative pop duo better known as They Might Be Giants, savor doing things just as they want them done, producing smartly crafted music whose influences range from polka and country to Elvis Costello and cartoon music.

"Freedom, as an artist, is really about doing something you think is good and not trying to second-guess what you're doing," says Linnell, the slight, typically low-key half of the duo. His partner Flansburgh, the more outgoing one, was unavailable. "Our music doesn't have a purpose. We're doing something we like. We just feel our way around without thinking too much."

They Might Be Giants, which plays the Maryland Science Center Saturday night, have stuck with that ethos for about 20 years now. And, for the most part, it has worked for the duo, garnering the Johns critical respect and a tight though modest following over the years. You may recall the band's biggest pop success, Flood, the gold 1990 album that spawned perhaps the group's finest singles: "Birdhouse of Your Soul" and "Istanbul (Not Constantinople)."

After putting out a popular children's album, No!, in 2002, TMBG returns to their eclectic rock-pop roots on The Spine, due out in July.

"This is album No. 10," says Linnell, 44. "I don't know if I can say how we've changed much. I think we're driven by the same impulses we had 20 years ago. The Spine is more of a return to what people like about us in the first place."

On the new album, you get 16 tightly produced, densely written songs, some of which the band will perform Saturday night. Musically, the feel is playful and wildly experimental - referencing such styles as '80s synth-heavy pop and Ramones-like punk. "We've gotten to do some more electronic stuff," Linnell says, who has written most of the duo's best-known songs. "We're trying not to define ourselves. We want to feel free to do what we want."

The wit, geeky humor and childlike wonderment - distinguishing qualities of TMBG's music since its 1986 self-titled debut - swirl through The Spine. Lyrically, as always, the content or story isn't always immediate. But the music is accessible, bristling with energy.

Linnell says, "What we like about what we're doing is the part that doesn't seem like it's directly derivative of any other band. We have existed on the margins."

He and pal Flansburgh grew up in Lincoln, Mass., a moneyed Boston suburb bordering Walden Pond. (The two are based in New York now.)

They met while in high school, sharing a strong love for music: Miles Davis, the Ramones, George Jones. In the early '80s, after dropping out of college, Linnell and Flansburgh moved to New York and formed They Might Be Giants, naming the group after the 1971 George C. Scott movie.

"It's just something we thought was cool," Linnell says of the name. "We didn't think we were gonna be called that for 20 years. There's nothing deep to be read into it."

The New York City punk culture, the guys' initial draw to the city, had died by the time they arrived. But TMBG was undeterred, eventually making a name for itself on the city's underground performance art circuit. The group's stage show at the time was interesting: just the two Johns -Flansburgh on guitar, Linnell on accordion - backed by a tape of rumbas, mechanical drum loops and synthesizers.

The group also had different but effective ways of marketing themselves at the time. The guys transferred some recordings to their telephone answering machine and advertised the result as "Dial-a-Song," which presaged the 900 numbers some artists use to promote new songs. Two years later, in 1985, TMBG put out their first release on flexi-disk, a floppy record they sold via mail order, at shows and sometimes nailed to trees in Tompkins Square Park. Such grassroots efforts kept the band working regularly for years before it snagged a major-label deal with Elektra in 1990.

"We sorta jumped the gun in bands finding another avenue - other than major labels - to promote their work," Linnell says.

Despite the commercial ups and downs, the creative energy between Linnell and his partner has not waned a bit over the years.

"We're lucky that it hasn't gotten harder to work together," he says. "It seems like by now we would have fallen out or gotten sick of each other. But John and I really understand each other very well."

Linnell adds, "We're kind of suspicious of the ideal that one would do better if one got rid of the other - even though we have done some solo things. We really share. We're not trying to get out of each other's shadow."

They Might Be Giants play the Maryland Science Center, 601 Light St., Saturday night at 6:15. The show is free and open to the public.