Violinists as conductors: Who needs a baton when a bow will do?

Conductors are discovering competition coming up, literally, from behind their backs and over their shoulders.

One after another, violinists have claimed music-director positions and guest-conducting engagements in some of the world's better orchestras. Leading from the concertmaster's chair, they don't necessarily hold a baton or reap the glory of their more Bernsteinian colleagues. But they're changing how music is made — and, perhaps, how it's heard.

"Each player has enormous responsibility," says violinist Nadja Salerno-Sonnenberg, who is in her fourth season as music director of the New Century Chamber Orchestra in San Francisco. "It's very democratic. Everybody has their say" in rehearsals.

"I've seen conductors stifle the players' natural impulses. Their attitude is, 'Don't look at each other. Just follow me,' " said violinist Joshua Bell, who made it clear that's precisely what he won't do Monday night when he leads the Academy of St. Martin in the Fields in Beethoven's Symphony No. 4 at the Kimmel Center. "I've watched a lot of conductors, I've seen what does and doesn't work. And sometimes less is more — letting people use their instincts."

That's exactly what Philadelphia Orchestra concertmaster David Kim did when he stepped up to lead the orchestra in Vivaldi's The Four Seasons after the scheduled conductor canceled at a "Beyond the Score" concert last year. "We just did it as we went," he said. And it went so well that he had a guest gig with the Chamber Orchestra of Philadelphia in December, will lead the Philadelphia Orchestra in Vivaldi during its Beijing residency, and has been entrusted to collaborate with eminent British pianist Imogen Cooper in an orchestra subscription concert next season.

"I'll be doing my regular job, without the conductor there," he said.

Oh really? Audiences might not see any great difference when Salerno-Sonnenberg leads from the violin, but she certainly feels different: "Everything you do is in HD," she said. "You can never rest during those measures when you're not playing. It never stops. You can't blink."

"You don't have to wave your arms constantly," said Bell. "Sometimes you just lean this way or that way. Or know when to give a burst of energy with a flick of the wrist."

Some violinists have plunged more decisively into conducting. Following the lead of violinist Pinchas Zukerman (now music director of Ottawa's National Arts Centre Orchestra), both Nikolaj Znaider and Thomas Zehetmair conduct full-fledged symphonic concerts in tandem with their violin careers. Zehetmair is even shaping up to be a revisionist: A recent radio broadcast with the St. Paul Chamber Orchestra featured a raw, volatile Schubert Symphony No. 9 — quite unlike what's normally heard.

For all the power that comes with the baton, there's a certain maneuverability without it. Expectations are less laden with protocol. Salerno-Sonnenberg, whose experience playing in an orchestra doesn't extend much beyond her high school ensemble in Cherry Hill, freely admits her leadership style is quite her own.

"I'm not the greatest at giving cues," she says. "But they know every single minute body movement of mine, and what it means."

Some conventional conductors can be technically unconventional, too, such as Valery Gergiev. "He has his own style, but it works," says Bell. "It starts with a conception of the music in your head."

For Bell, 90 percent of the performance is conceived in rehearsal. And there's a lot of conception on his part: His approach toward Beethoven is based on his own hybrid version of historically informed performance.

Kim is more oriented toward the heat of performance; his percentage is more like 50 or 60 percent: "The adrenaline and institutional pride kicks in and pow! It just pops in that moment."

He's one of several Philadelphia Orchestra violinists who lead ensembles on the side. Luis Biava retired from the orchestra to become artistic director of the Temple University Symphony Orchestra. The late Irving Ludwig spent post-retirement years leading the Lansdowne Symphony Orchestra. Davyd Booth leads orchestras at the Temple University prep department — and he never took a lesson.

Besides knowing how to demonstrate what they want, violinists-turned-conductors also know orchestra psychology. No extra chitchat or cutting short rehearsals. "The players either have to like you a lot or hate you. It's one extreme or the other. It's the intensity of both feelings that bring out the best playing in people," said Booth.

So much can be learned from the rank-and-file view of an orchestra that some star violin soloists stick around after their concerto and ask to play in the back row for the second half. That doesn't always go over well. When Zukerman, then at the height of his stardom, made such a proposal to the late Georg Solti, the reply was blunt: "Do you know the piece?" Bell, in particular, is wary about seeming presumptuous.

In any case, chamber orchestras are often happy to accommodate a less-than-seasoned music director if the rapport is good. The result can be a democratic style that yields performances that seem ignited from within. Also, the orchestras certainly benefit from the higher profile that comes with a starry leader, which can be a trump card for establishing an electronic-media presence. Though the Academy of St. Martin in the Fields was one of the world's most-recorded orchestras during the 1980s, without Bell it probably wouldn't be in the midst of a multiyear Beethoven symphony project with Sony Classical. Kim's concert with Chamber Orchestra of Philadelphia was beamed across the country via SpectiCast. Salerno-Sonnenberg hadn't even heard of the New Century Chamber Orchestra before being approached by its management. But since her arrival, the orchestra has issued two compact discs and a DVD documentary, On Our Way: The Journey of Nadja Salerno-Sonnenberg and the New Century Chamber Orchestra.

But such feats aren't as easy as they look. "Sometimes I'll come out of a double-rehearsal day and have to change clothes to go to some cocktail party to meet donors. That's the part of the job I wasn't expecting," she says.

As their careers progress, the baton seems to loom over them like Macbeth's dagger. Bell admits that once he gets to the later Beethoven symphonies, he'll probably need one. Salerno-Sonnenberg already has one — her mother picked it up for her at a garage sale. And what happens when careers progress to larger orchestras that expect some semblance of a baton? Salerno-Sonnenberg is finding out this very weekend in a guest engagement with the Westchester (N.Y.) Philharmonic.

"It may be challenging," she says. "I might do something with my left eyebrow and they won't know what the hell it means."

Contact David Patrick Stearns at dstearns@phillynews.com.

Music?Academy of St. Martin in the Fields?7:30 p.m. Monday at the Kimmel Center, Broad and Spruce Streets. Tickets: $29-$96. 215-893-1999 or www.kimmelcenter.org.