JUST BEFORE the beginning of most orchestral programs, concertmaster, traditionally the last man to come onstage before the conductor, stands up, turns toward the center of the orchestra, and nods his head. A moment later, a thin, reedy sound emerges. It is the voice of the oboe, giving the orchestra its official note for a final tune-up.

Why the oboe?

Ronald Roseman, virtuoso oboist for over two decades, was in town recently playing with the Juilliard Quartet at the Library of Congress and talking about his difficult and lovely instrument. "Why does the instrument sound that A? I've no idea," he said, and then went on to surmise: "Maybe because the tone carries, the sound is easy to hear, it's very focused. And the oboe doesn't tend to vary very much, so that the A will come out very much the same every time." (Some orchestras have been experimenting lately with electronic devices for their A, and a few follow the European tradition of tuning up backstage, thus denying audiences of the special joys of hearing the strings and winds in full cry as they match their A's to that of the oboe.)

If you ask Roseman, "What is hard on the oboe?" the first thing he mentions, and the subject that occupies him more than any other single aspect of oboe playing, is reeds and the reed.

"Probably the hardest thing about the oboe is the reed. And tone color. And control." The reeds are made by the musicians themselves. "I start with the tubes of cane -- the ones they used to make fishing poles out of. I buy 8-inch canes from France. Everything from that to the finished reed is done by me. It's a very complicated process.

"The cane has to be a certain diameter: 10.5 millimeters. If it's 11, the opening of the reed will not be enough, unless you live in a very humid climate or it's a damp time of year.

"When you have the opening just right, you split it into three segments with an evil-looking device that looks like an arrow. At that point you throw away about two-thirds of it. It may be either the wrong diameter or something else. You have a machine that cuts it to size. Then you run it through a planing machine. You gouge it until it's approximately 60/100th of a millimeter in the middle and 45/100th on the side. If there's a difference of 5/100ths, it will be basically useless. The tolerance is very small.

"Then you have to put it over a form, you bend it over, and run a knife down the side so that it takes the form of an oboe reed. Then you tie it on a cork with a brass staple in between -- tie it on with something like fishing line, nylon -- and you have something that looks like a reed. Then the reed has to be scraped. There are two schools of thought about making reeds. One school makes reeds very quickly -- in about 20 minutes and then they use them right away for about an hour or two.

"I do the opposite. I make the reeds over a period of maybe five workings.

If it's a reed for orchestral work, for woodwind quintets, maybe 10 -- and for solo playing, maybe as much as 15 or 20 times. I do a little and let the reed break in.

"The reed really has to do everything for you in order for you to play your best. In performance you have to keep them wet. As soon as they dry and then every time you take them out of your mouth you keep them wet.

"All this is part of the American school of oboe playing started by Marcel Tabuteau [the longtime first oboist of the Philadelphia Orchestra]. It really emphasizes tone color. There may be areas where so much care is not taken with the reed, but in order to get a rich round sound, the reed is very important. It's like the combination of the bow and the violin.Even if everything else is right, if the reed is wrong, the sound will not be right.

"The standards of playing today are miles above what they were: Twenty years ago low notes weren't coming out right, high notes weren't coming out, and sometimes middle notes. Tabuteau taught a whole generation: Bloom, both Gombergs, Mack, DeLancie, Lifschey. The first time I heard Bloom I couldn't believe anything could be as gorgeous as that. Since then we have worked hard in teaching and maybe my generation do each aspect, so that now a student studying with someone like myself or Mack knows at the end of four years how to play the instrument -- how to make a reed that works properly, that's balanced right, how to breathe properly."

Breath control on the oboe? Is that hard?

Roseman took on the happy look of a man who has just heard a question he was waiting for.

"You have to spend a lot of time on breath control. I give specific breathing exercises. I have my students lie on the floor and teach them how to breathe with the diaphragm and the intercostal muscles, then with the chest, but they shouldn't use the chest.Because the oboe reed is so small, people tend to get a lot of strain. Playing requires force but not strain."

Do oboe players play longer phrases on one breath than other players?

"Right. The reed is small, so a very small amount of air is required for volume and you can play a very long phrase. As a matter of fact because of that, you have an extra problem in Baroque music which has the longest phrases. You have to mark the places where you breathe out as well as where you breathe in, because you don't get rid of your air sufficiently. So I mark my music 'out/in.'"

What about vibrato?

"You have to play with vibrato. To play the oboe without vibrato is like playing the violin without vibrato. Many teachers do not teach vibrato, saying that it should come naturally. Well that's well and good, but it only comes naturally for one out of a hundred -- the other 99 have to be taught.

"I teach my students how to do a diaphragm vibrato. Sometimes it may take a year, but at the end of the year they can vibrate when they want to vibrate. They can start a note without vibrato and add it. It's all a matter of control."

What are the famous test passages for oboe, the ones students are told to have ready for auditions?

"I tell my students the "Tombeau de Couperin,' by Ravel, Debussy's 'La Mer,' the 'Scala di Seta' overture by Rossini because of the staccati, the funeral march from the 'Eroica,' and the opening page of 'Don Juan.' That one's fun even though no one ever hears it. But you have to be able to play it! Also from 'Don Juan,' the long solo. Maybe the Scotch Symphony of Mendelssohn. Those are the hard ones. They may go well 20 times and then the 21st time something happens."

Roseman said he has been lucky in his career: "I started out as a chamber music player, but I've done solo recitals since I started, free-lance work in New York, played with the Little Orchestra Society. Then I went to Aspen where I played in the festival orchestra and then for about five years I was acting co-principal for the New York Philharmonic. I was very lucky to have done a lot of everything, even playing shawm in the New York Pro Musica in that original wind band Noah Greenberg put together."

How about the future of the oboe -- are solo recitals on the horizon?

"Oh, I think so. We have as good repertoire as the clarinet and the flute. There's a wealth of baroque and a lot of contemporary stuff being written. When you have people who really play the instrument beautifully and composers who want to write, the public wants to hear it."