When Marc Anthony listens to music, he can't sit still. He does a little samba in his swivel chair, flutters his hands rhythmically against his thighs.

"This first song will be the opening; it's called 'When I Dream at Night,' " he announces, playing a few tracks from his new album. He pretends to saw soulfully at a violin as the strings swell in a crescendo.

"My absolute favorite song," is his intro to the next number, a ballad he co-wrote for his 5-year-old daughter. He mouths the words, taps his cheap plastic flip-flops on the floor.

He's in Studio D at the Sony complex on the West Side, a wood-paneled room with a vast, complex soundboard that looks as though it could launch missiles; it's where, in fits and starts over the better part of a year, he recorded the CD "Marc Anthony," which hit stores last week.

"D as in dog," says his friend Jennifer Lopez, who's hanging out in the rear of the studio, eating a takeout lunch.

"D as in dinero," Anthony returns, joking. Sort of.

This CD actually deserves the phrase much-anticipated. Anthony can sell out arenas on several continents, pack Madison Square Garden and make history with the way his albums fly up Billboard's Latin music charts--but that all barely got noticed by the somewhat insular American mainstream. He's been a salsa singer who records primarily in Spanish, and in this country, in music as in other art forms, you use English if you want to make a serious dent in the culture. Industry insiders and smitten critics have been waiting for the rest of America to discover him.

Claimed as a local hero by both his native New York and his ancestral Puerto Rico, Anthony contemplated an English album for at least three years. But he got waylaid by his own good fortune as he starred in Paul Simon's 1998 Broadway musical "The Capeman"--the first time many Anglos paid attention to the skinny guy with the astonishing tenor--and then spent months shooting Martin Scorsese's new movie, "Bringing Out the Dead."

But now, a couple of weeks past his 31st birthday, here it is, with the first single shooting up the pop charts. For a musician whose fans are prone to flinging Puerto Rican and Dominican flags to him during concerts, a non-salsa album in English might have stirred some talk about musical crossover and cultural assimilation whenever it was released. To have it hit in the midst of this supposed Latin Moment, when a wave of Latin artists who record in English (Lopez, Enrique Iglesias, Ricky whatsisname) are getting splashed on magazine covers, makes the transition even trickier. Columbia Records and another Sony division, Sony Discos--which have signed him to deals said to be worth more than $40 million for both English and Spanish recordings--stand to make, or possibly lose, a whole lot of dinero.

The subject of crossover and competition makes Anthony wince, roll his dark eyes, draw as close to uneasiness as a guy who's famously friendly and unassuming ever gets, at least in public. Ask him to describe the album and he sighs and swivels his chair for a while. "That's the hardest thing to do," he says. "I don't know. It's just the best music I can make this year."

But when he's not being pressed to offer characterizations or hold forth on the Latin Moment, when he can simply yield to the music, he's a happy man. There's a passage in the ballad "Don't Let Me Leave" that makes his fingers twitch. "That guitar," he breathes reverently. "It sings."

'RAW TALENT'

In concert, Anthony has an entire repertoire of movement, many personas. He's a dervish who dances maniacally as the salsa sizzles, a romantic clutching his heart when the tempo slows, a master showman who can strut one moment and roll across the floor the next. But he also communicates stunned disbelief at what's happening to him; at the Garden last year, with flowers raining down on the stage, he often clapped his hands to his temples and shook his head, as if he were the birthday boy and 19,000 or so fans had just jumped out yelling "Surprise!"

But maybe it's not entirely a surprise.

He was barely in grade school when he started belting out songs from atop the kitchen table; his father, a jibaro, or country musician, replicated the musical gatherings of interior Puerto Rico in their East Harlem apartment on weekends. "I thought everyone's friends came over on Saturday and brought their guitars and bongos," Anthony says. He was 10 or 11 when he informed his mother, "I'm gonna sell out Madison Square Garden one day, and you'll be queen for the night."

Still in his teens, having adjusted his name from Marco Antonio Muniz to avoid confusion with a Mexican singer, he was singing in pocket-size clubs, producing and writing songs for other musicians. Just as he was about to enlist in the Air Force (his unimpressed mother had pointed out that his music wasn't paying the bills), Anthony landed his first recording contract.

Salsa, a percussive urban brew of Cuban and Puerto Rican forms with jazzy improvisational flair, was hardly hip when Anthony first felt drawn to it a decade ago; it was nostalgic, parents' music. His dance tunes had relied more on synthesizers and drum machines than on horns and congas, and he sang them in English. The salsa world, province of bands in matching suits, was equally suspicious of this ponytailed novice in jeans.

But he could sing. His three salsa albums broke sales records and won a raft of awards and hosannas; Time magazine, voting "Contra la Corriente" one of the 10 best albums of 1997, called his voice "a flash of gold." He soon required bodyguards to keep fervent fans from engulfing him on the streets of Spanish-speaking neighborhoods. By the time Simon's show "The Capeman" was about to open, with huge posters of its three popular Latin stars (Anthony, his longtime hero Ruben Blades, his friend Ednita Nazario) plastered around Times Square, Billboard columnist John Lannert could say that "Marc Anthony, in New York, is God"--and not sound wildly off the mark.

In the non-Hispanic world, however, it might have appeared that an unknown musician was being "discovered," a show-biz fairy tale with Paul Simon wielding the magic wand. Certainly Anthony was thrilled to be involved. He'd just returned from a tour ("Japan or something") when Simon first invited him to his apartment on Central Park West. Simon spent four hours talking and playing songs about a Puerto Rican kid named Salvador Agron, who'd figured in a famous murder of the '50s.

"This is Paul Simon singing in my ear! How cool is this?" Anthony remembers thinking. It was a confusing encounter nonetheless. "As I'm leaving, putting on my coat, I said, 'One question. What am I doing here? What was this all about?' " Simon's response, he remembers, was, "To get your opinion of the music. And see if you were interested in being in it. Being Sal."

He was, investing more than two years in the project as it slowly wound toward Broadway. Yet Anthony was amused at the way critics and the Anglo media regarded him. "What they saw was a seasoned veteran they thought was a beginner," he muses. " 'Wow, this kid has raw talent!' No, it's polished craft, but you've never been exposed to what I've been doing for the past seven years. You just didn't see it."

Though "The Capeman" swiftly closed--the critics were brutal--it did showcase Anthony before a broader audience, including music execs. "Once people heard him and got a sense of him, the frenzy started," says Don Ienner, president of Columbia Records.

What the business saw was partly a marketing opportunity--"The recording industry has been missing an incredible male vocalist for many years," Ienner says--and partly a talent that could transcend language. "There's a certain emotion with Marc: When he opens his mouth, whatever the lyric, you believe what he says," Ienner explains. "If he sang the phone book, I'd believe him, too."

True, Anthony's most distinctive trait as a performer isn't conventional sexiness, though he's frequently referred to as a "salsa heartthrob." It's intensity. Let hunky Ricky Martin, whom Anthony's known since Martin's days as a teenage pinup in the kiddie vocal group Menudo, play the hip-twitching stud. Anthony is almost disturbingly thin, angular-faced; he used to wear a pair of spectacles but jettisoned them after recent eye surgery. He grew a scruffy beard for "Bringing Out the Dead" (opening this month) that made him look even more boyish than usual. He portrays emotions from lovelorn suffering to wild exuberance with convincing fervor--which is why he's made an impression in such movies as "Big Night," though he's never studied acting.

"He is a very natural actor," says casting director Ellen Lewis, who suggested to Scorsese that a homeless man, a part originally written for an African American, could be played by a Nuyorican. "This character was definitely a stretch, playing a psychotic guy. But something in the character projects a great deal of soul, and that's something Marc projects."

'NOT A SIZE ISSUE'

What if "Marc Anthony" and its first single, the twitchy "I Need to Know"--which has rocketed into Billboard's Top 10--had come out a year ago? Before Martin lit the fuse with his performance on the Grammy Awards, before the magazine stories about "La Explosion Pop Latino"? The album might have sunk or soared, but at least it would not have made Anthony seem part of a trend. He doesn't appreciate being seen as one of an undifferentiated clump of Latino singers on the make, seeking fame and fortune in English.

"It's not that I want to be bigger," he's saying, his bare feet propped on a French Provincial chair in a hotel suite where he's playing meet-the-press. A couple of weeks have passed and he's just back from an experience so rare--a vacation, in Puerto Rico--that the idea of crossover calculation feels silly; he's pretty blankin' big already. "Are you kidding me? I can't say I'm the most comfortable with fame as it is. It's not about grandeur. This is not a size issue."

To Anthony, the decision to make an album in English is perfectly simple. It was the first language he spoke or recorded in; he added Spanish only at his father's insistence. "The rule in my house was, certain days of the week my dad would talk to us in English and we had to answer in Spanish," he recounts. "He felt it was his responsibility, and thank God he did. It just gives everything a different meaning." And it made an international salsa career possible. But in his private life, Anthony is completely bilingual. English is "just as big a part of me" as Spanish, and singing in what is actually his native tongue seems a natural thing, "not a career move."

But it is, inevitably, a career move, too. Latin music--defined as albums that are more than half Spanish-language--has chalked up several years in a row of phenomenal growth, according to the Recording Industry Association of America. It's selling because the Hispanic population is growing, because Spanish radio stations in major cities are grabbing larger shares of the market, because albums are increasingly sold through large retail chains as well as small neighborhood stores. And because people, and not only Hispanic people, like it.

"Latin music and culture are starting to permeate the mainstream; you can see it in movies, advertising--they all feed off each other," says Ricardo Dopico, who runs the RIAA's recently opened Miami office--itself testament to the music's importance.

But there's a limit; Latin music still accounts for only about 5 percent of music sales. "This is not a country that's ever going to embrace hit singles that aren't in English," observes Lannert, who writes Billboard's Latin Notas column. "The music can have Latin elements, but all these artists are making their mark with English-language recordings."

How will Anthony's intensely loyal followers react, not only to an album that's mostly English (just three tracks are in Spanish) but that is distinctly not salsa? "Marc Anthony" is mostly a collection of power ballads, produced and written by some of the same people who confect them for Celine Dion and the like. He's confident his fans will follow; most are bilingual anyway (some younger Latinos barely understood his Spanish lyrics) and his non-Spanish-speaking audience is growing. But any artist takes a risk when he changes musical directions. "Just a pleasant album by a singer who on past releases has proved himself capable of greatness," wrote a disappointed critic at Time, hoping for more salsa or at least "edgier" pop next time out.

"I'm not convinced all those salsa fans are going to follow him over to the pop side," Lannert says. On the other hand, some people encountering him for the first time will be won over. There's no formula for this kind of linguistic and musical border-crossing, no model to follow--except for the pattern that artists inevitably get restless. "He could do salsa forever and do great; he wants to do something different," Lannert assesses.

Anthony, pointing out that all his supposed competitors are longtime friends, wishes people would stop trend-spotting and forecasting--and simply listen. He considers this album "1,000 percent more personal" than his earlier ones because he wrote many of the lyrics, which allude to such subjects as his daughter, Arianna, and his parents' divorce. (He himself is single since his relationship with Arianna's mother ended and another relationship faltered.) Which category the album falls into matters less. "Don't buy my music because I'm Puerto Rican," he says wearily. "Buy it because you like the music."

'TO WALK AWAY'

Earlier this year, Anthony moved from the Upper East Side to hipper TriBeCa, no small thing. From his old high-rise on East 92nd Street, he could gaze down on El Barrio, East Harlem, on "my whole childhood--my elementary school, my junior high, the first apartment I lived in, the bridge where I had my first kiss. My whole life from that window." Yet at 30, "it wasn't hard to walk away from." Perhaps it was simply time. The last couple of years have marked, in general, a period of change.

After more than a year, for instance, he also managed to emerge from a punishing legal fight that erupted when he tried to leave his old salsa label, RMM. Sony, Columbia's parent, had to grease the process with cash. Dance-driven salsa is a young man's game--few stars endure past 30--so perhaps time was an element in that change as well.

Then there were Anthony's adventures onstage and on camera. The people involved in "The Capeman" were icons to him, sources of inspiration. Ditto the Scorsese movie, which stars Nicolas Cage. "I enjoyed just sitting on the set, watching everybody and learning, studying. Fascinating, fascinating, fascinating." If those detours from music kept him from touring, from releasing this album earlier, he is not sorry. "If that's a sacrifice," he says dryly, "I could live with that kind of sacrifice."

Still, music is what compels him most, and has since he was small. As a little boy, "I used to stutter, really badly," he remembers. Singing was the easiest way to make himself heard; "when I sang, I didn't stutter."

He credits his mother with spooking him out of his affliction. Anthony's affection for and gratitude to his parents is palpable; he tells with pride of the new apartment he just bought his father in San Juan, of his mother's travels--now that her eight children are grown--from Acapulco to the Bahamas to Miami and around again. In concert, he's been known to sing a duet with his father, or introduce his mother ("mi mami!") in the audience, then kneel on the stage in homage--not your normal pop-star stance.

She was standing with him at a bus stop, years ago, when a man walked up seeking directions. The man stuttered, too. "It took him 15 minutes to ask which bus to take," Anthony remembers. "He was making faces, and I was just staring. It was really, really bad. When he walked away my mom said, 'That's what you look like.' And I never stuttered again."

Nonetheless, this is not someone who takes self-expression, in any language, for granted. Whatever movie roles and other welcome distractions come his way, he doesn't intend ever to stop singing.

"It's exhilarating," he says. "When I sing, I feel like everything I've ever wanted to say, in my whole life, is about to come out of my mouth."

CAPTION: Marc Anthony: "When he opens his mouth, whatever the lyric, you believe what he says," Columbia Records President Don Ienner says. "If he sang the phone book, I'd believe him, too."

CAPTION: Marc Anthony calls his new album "1,000 percent more personal" than his earlier ones.