They are a special breed, like player-managers in baseball. To perform on an instrument and lead an orchestra at the same time requires switching back and forth between two very different sets of skills. Violinist Pinchas Zukerman will display those skills with the New York Philharmonic on May 12-14, when he simultaneously plays and conducts Bach's Brandenburg Concerto No. 5, then appears as violin soloist in Stravinsky's Histoire du soldat under the baton of the Orchestra's Assistant Conductor, Xian Zhang. The program opens with Mr. Zukerman conducting the Brandenburg Concerto No. 3 with Philharmonic Principal Flute Robert Langevin and Harpsichordist Lionel Party as soloists.

During the 2005-06 Philharmonic season, violinist Itzhak Perlman and pianists Christian Zacharias and Jeffrey Kahane will repeat the feat, playing and conducting Mozart works, and leading other pieces on their programs. All have held conducting posts with major orchestras, and all defend playing-conducting as an artistic choice and a separate skill in which listening is perhaps the most essential ingredient. "I started when I was eight," said Mr. Zukerman, "not conducting, but playing chamber music and learning the process of listening."

Mr. Perlman told Susan Jackson in a Playbill interview last season that his playing, conducting, and teaching all feed each other: "I learn to see things from different perspectives and listen with different ears. In all three of these things, the most important thing that you need to do is really listen."

But there are limits to this collegiality for even the most gifted musician. Of his upcoming program with the Philharmonic, Mr. Zukerman observes: "There was no question of my conducting and playing the Histoire du soldat. There's too much going on musically, plus a narrator, and staged action. You have to have a conductor."

Mr. Zukerman was referring to what could be called the Great Divide of playing-conducting: the small orchestra of the 18th century, which was often led by an orchestral player (frequently the first violinist), versus the expanded ensembles of Beethoven, Berlioz, and later composers, which required a person standing on a box with a stick to hold it all together.

Jeffrey Kahane has recorded Beethoven's five piano concertos and Mendelssohn's two, which he conducted from the piano; but even he declined to lead the orchestra in the slow movement of Beethoven's Fourth Concerto, with its dramatic dialogue between orchestra and soloist. "I asked the concertmaster to do that," he says. "It's actually more powerful without a conductor." Christian Zacharias adds that "the concertos of Chopin are about the limit," after which the orchestra has too large and complex a role to be managed from the keyboard. Mr. Zukerman has his own cutoff point. "When there are four horns," he says, "I can't conduct them and also play the violin."

All agree that conducting is a separate discipline from playing their instruments. "I've seen some great instrumentalists who thought they could conduct by just waving their arms, and it was a catastrophe," exclaims Mr. Zukerman. "You have to show respect for your instrument, and conducting is an instrument. To learn it takes a lifetime. You mustn't conduct if you don't know how to do it!"

Conducting is also a big psychological change from the solitary life of the touring virtuoso. "It means you open up toward a group of people," said Mr. Zacharias. "You have to face them and try to convince them of your ideas."

The transition from player to conductor takes place at different times for different musicians. "I took conducting classes at Juilliard," said Mr. Zukerman, "but I think I learned more from playing concertos with the great conductors‹Munch, Szell, Barbirolli, Kubelìk, Giulini, Lenny [Bernstein]. I watched how they worked, and I asked them a lot of questions."

Mr. Kahane foresaw a conducting career while still a student at the San Francisco Conservatory in the 1970s, but owing to his early success in international piano competitions, "my conducting aspirations went on the back burner," he says. "But in 1988 we were doing the Mozart G-major Concerto at the Oregon Bach Festival, and the director said to me: 'You know this piece so well, why don't you conduct it?' We did it as if it were a chamber-music work. I think for all of us who do this," Mr. Kahane adds, "the philosophy is the same: to foster a chamber-music atmosphere."

Mr. Zacharias, too, enjoys the intimacy of simultaneously playing and conducting: The orchestra players, he says, "will watch a conductor, but when you also play with them, they are listening to you. They are fine musicians too, and they give you something back." He admits, laughing, that "sometimes I am so carried away by something beautiful that the orchestra did, I almost forget to play!"

David Wright was formerly Program Annotator of the New York Philharmonic.