Following the music

"I need some me time," he says, smiling as he walks through Porter Square during a break from a Boston Modern Orchestra Project rehearsal. "And people have plenty of times to get in touch with me."

They do? Gazing over his schedule for a recent week, it's hard to imagine the cellist sitting by the phone. There were at least two rehearsals a day, sometimes three; concerts on Monday, Friday, and a Saturday; and a series of late-night recording sessions in Milton.

When the seemingly omni-present Popper-Keizer is not spotted at a particular rehearsal or concert anywhere, "the joke is, where's Rafi?" says composer John Harbison.

In a musical city driven largely by an unsung network of hard-working and underpaid freelance musicians, Popper-Keizer might be the most easily recognized. With his long hair and thick beard, the cellist has become a familiar face whether in the center of a large orchestra or as a lone player tackling one of Bach's most difficult solo works. Tonight and Sunday, Popper-Keizer will take part in Emmanuel Music's performance of J.S. Bach's St. Matthew Passion. Tomorrow, he'll be performing with Bernadette Peters. His month also includes concerts with the Boston Philharmonic Orchestra and Boston Lyric Opera.

That versatility is, in part, why Popper-Keizer is in such demand.

"He's solid in every respect and such an intelligent musician, too," says Gil Rose, BMOP's artistic director. "When we need a cellist, he's our first call."

Harbison says Popper-Keizer's enthusiasm rubs off on other players.

"Everybody wants him because not only can he play fantastically well but he has a spirit that makes everybody else want to be that dedicated," says Harbi son. "And you know, he never seems tired. Once he sits down around the instrument, he and the instrument have such a rapport and he's so committed to being there, I don't think anybody within a radius of Rafi is going to give any less than 110 percent."

Freelancing is not an easy life. It's highly competitive, and even the best players can struggle with their bills. Popper-Keizer and his wife, Geneva, have one car, a used Camry. They rent an 880-square-foot apartment in Cambridge, the first floor of a triple-decker. A harpsichord and piano sit in the front room, and the couple shares a bedroom with their two children, daughter Bronté, 20 months, and son Kai, 7, whom Geneva home-schools. Popper-Keizer's schedule can be hard to predict. He works anywhere from 10 to 80 hours a week. His take-home for last year: $36,640.22. That's about a quarter of the starting salary at the Boston Symphony Orchestra.

"I'd love to make three times what I do now but I'd much rather be happy and making enough to live with," he says.

For Popper-Keizer, that attitude comes, in part, from his upbringing. He grew up in Santa Cruz, Calif., known as much for its population of left-leaning social activists as its beautiful coastline and redwood forests. He was deemed special early on by his parents, who realized the boy was reading street signs not long after his first birthday. By 5, he was reading at the level of a senior in high school.

And at 10, he began taking classes at the University of California-Santa Cruz before enrolling, at 12, as a full-time student.

The boy had a particular gift for math and science, which pleased his father, Lewis Keizer, a former Episcopal priest, educator, and the onetime director of the Santa Cruz Chamber Orchestra. But he had a love of music, which his mother, Tess Popper, who plays flute and has studied music, encouraged and nurtured. Even now, his father says he was disappointed when Popper-Keizer, around his 14th birthday, told him he was going to devote himself to music.

"It's a horrible way to make a living," he said in a telephone interview. "I didn't want him to be confined to his physical body. When you play cello, it's just like a baseball pitcher. There's a time you start to lose your muscles. I wanted him to have more options. I felt he could be a musician along with other things. He could have done a double major. But he really wanted to do just music. His mother kind of became the advocate and I kind of gave in."

By graduation, in 1994, Popper-Keizer had become well known for his playing. Just 17, he scored a position as a graduate teaching assistant. That's when he met Geneva, then 22.

"He was the star of the school and I saw him walking and somebody pointed out, that's Rafi Popper-Keizer," she remembers. "He always wore an overcoat, and this is in California. And you know, the hair. So he's walking down the hall and he's conducting in the air and singing to himself and I had seen his name on a poster on the wall. I swear to God I didn't think he spoke any English."

Studying with Popper-Keizer, she discovered that the intense, quiet musician was actually quite shy and socially awkward. They became friends, though she held off from dating him until he turned 18. But in 1995, within six months of going out, they were married. Not long after, Popper-Keizer moved across the country to attend New England Conservatory. He spent two summers at the Tanglewood Music Center on a fellowship and began building his freelance career.

"When you first start out, you have to take anything that comes along," Popper-Keizer says. "When you're in a great orchestra, it's amazing. When you're in a dysfunctional orchestra, it can be terrible."

Over time, he discovered that he did like playing with larger groups. Playing a Mahler symphony, for example, provided a kind of spiritual lift unavailable in a chamber group. But there were limitations. Orchestra players, he concluded, need to suppress their own style. That made him rule out trying for a full-time gig.

Juggling all of his commitments is not always easy. Popper-Keizer knows he has to give certain organizations - BMOP, for example - enough time to keep the group's playing consistent. He also wants to remain true to his love of smaller groups and solo performances. One thing hasn't changed since his arrival in Boston: Popper-Keizer is averse to self-promotion.

"He's old-fashioned in the sense that he honestly feels his music should speak for itself, and if people want to hear him play, they will," says Geneva. "People have been constantly telling him he's got to get representation. He won't. He's very against that. He hates parties. He hates the surface socialization. It doesn't speak to him. If someone asks how you are, you don't say fine. You really tell them how you are."

If her husband had his way, he would likely play in a chamber group that made recordings and played and didn't tour much. "He just wants to play music," she said. "That's what keeps him happy and that's what keeps him alive."

Popper-Keizer says he doesn't have a scripted sense of how to proceed from here. He loves playing with lots of musicians. But he also appreciates solo recitals such as the one he was to give at Emmanuel Music yesterday, Bach's Suite VI in D major.

"Some weeks I'll be playing with 50 or 60 people," he says. "Others, I'll play with one or two. I'm going with the flow. I don't plan. Why would you need to plan?"

Geoff Edgers can be reached at gedgers@globe.com