THE HEADLINE read: "President and Mrs. Truman Attend National Symphony Opening." It was the third week of October 1954, in Constitution Hall and the timpanist, playing with the National Symphony for the first time, was Fred Begun. The review was complimentary.

Twenty-nine years later, at 52, Begun is the most visible man in the orchestra after the conductor. His chair, smack in the center at the rear, raises him above the other players. Begun says, "In our shop-talk, we sometimes consider ourselves the conductors from the rear. There is a kind of collaboration that has to take place. And, with a conductor who has the proper regard for the timpanist, as Slava does, the conductor trusts him to do certain things while he is tending to other parts of the orchestra. To make sure that the tempo is right, that an accelerando or a rallentando is happening without making him have to worry too much about it."

Majesty in the opening of Brahms' First Symphony depends upon the timpanist's imagination. Begun says, after recalling that Stokowski liked to have the powerful low C's doubled an octave lower than written, "I use two drums in order to get the best sound. That way you can play rounder without forcing. You don't want it too jabby -- something more mellow."

To illustrate, his arms move in graceful, oval-shaped figurations, with the sticks striking the identically tuned drums in a perfect beat for the great phrases. (There are nine pairs of sticks in his case, giving him a playing range from the shortest, tightest staccato to the most leisurely soft legato.)

As he plays, the famous body-English begins. Lithe, intense and dark-browed, Begun has been, for decades, one of the favorite sights for NSO listeners as he moves in the rhythms of the music at hand.Playing the Brahms, he takes on an imperious look, knowing how vital his contribution is to the entire episode.

"If you want something very articulate, rapid, then you play very close," he says. "It is very difficult to play that way from a distance. Height alters the sound. From a distance you're getting a sweep -- you're not stifling it, not choking."

When he talks about his drums -- and Begun makes a point of calling them that rather than timpani -- he shows the knowledge and love of a man who has written a book about timpani (they used to be called kettle drums) and how to play them.

"I usually use four in an average concert. You've got these components in the drum. The pedal (which changes the pitch of the drum). The bowl, which is suspended in a frame. There is a drum-head which goes across the bowl, and there is a counterhoop on top which goes over the edges. This, in turn, is fastened by eight rods to a spider mechanism underneath the bowl." The bowls are made of hand-hammered copper. A set of four, weighing around 1,200 pounds, costs more than $10,0000. There is a fifth bowl Begun calls his "piccolo," which he only needs for special music like the concerto written for him by Robert Parris. Begun will play that concerto with the Alexandria Symphony Orchestra next February.

As he plays, Begun is striking fairly close to the edges. But what happens if you strike it in the middle? "It's dead," he says, illustrating. "Now, strangely enough, that's a sound that Aaron Copland likes. That's a sound I've had to give him -- in "Billy the Kid" -- very dry. He's notorious for not wanting a note to ring."

"The drum heads are Mylar plastic. We don't use skinheads nearly as much as we used to. Calfskin is still the best quality sound, but the quality of the material has deteriorated. How long does a set of these heads last? if you're lucky enough to get the proper equation, for the rest of the season. Maybe a season and a half. These are mellowing out right now." The diameters of Begun's drums range from 30 inches down to the 20 inches of the piccolo.

"The use of the pedal goes back to [Richard] Strauss' time. He was one of the first to really use the chromatic changes. You find them in all the tone poems -- 'Don Juan,' 'Death and Transfiguration' -- he uses changes quite frequently. You'll be playing C, D over here, and a B flat is coming. Sometimes you have to make the change while you're counting, while you're playing. You do it with your ear and the gauge."

The gauge? Alongside the head of the drum there is a bright, semicircular metal gauge calibreated to a half dozen different pitches. When the timpanist uses the pedal on the drum, an arrow on the gauge moves to indicate the new pitch. It is one of the remarkable mechanical aids that help the player through a concert.

"There is also this hand control," Bergun says. "Say you've gotten the head in tune. This hand gadget is a fine-tuner. You can take the pitch down a bit with it or make it sharper. But it does not alter the pitch you have set with your pedal. You have to temper the pitch with the orchestra. In a softer passage, soft notes on the drum tend to sound sharp. You have to temper the note and, depending on how much, you do it either with the pedal or with a quick adjustment with this hand control.

"The next passage may be a little louder, and you have to vary it again. Pitch depends on many things: the humidity, for instance." (Anyone who doubts the effect of humidity should have seen the puffs of steam it was causing to blow from the vents above the stage at last Wednesday's concert.) "Other matters affectging pitch include the temperature in the hall, whether you are playing with the high wind instruments or the low winds, or just strings alone. You have to zero in on what part of the pitch is going on at that time. The drum is a very sophisticated machine."

"You work the pedals with both feet. In the Bartok Violin Concerto -- if you're sitting, and I only sit when I've got to do some very complex pedaling -- you've got the pedals working out just right. I use one foot to balance myself, say my left foot, while I use my right foot here on this drum. bFor example, let me play a couple of chromatic passages from the Bartok Concerto for Orchestra." Suddenly Begun's feet begin a dance of incredible complexity as his sticks rove over four drums. "In that passage you are playing 10 different pitches on four drums. That's a real kind of footwork.

That passage has become a famous audition piece."

What are the others? "Well, 'Sacre' of course" [the notorious "Sacre du Printemps" by Stravinsky]. But there are other things you select from the standard repertoire -- some of the Beethoven concerti. Take the end of the first movement of the third piano concerto. It's C, G, C, G, C, etc. What you want to hear is the misterioso." Again an illustration recalling the whispered mystgery of the closing measures. "That's color. By hearing just that much you can tell what the guy auditioning has even before you hear him play one bit of technique. You know whether he's a musician or not."

In an average concert, the timpanist may be very busy for quite a stretch and then have nothing to do for minutes but to sit there and be sure he is ready to come in at exactly the right moment. "It's one thing when you know a piece, but there are those things that are never safe. You've got to be sure about one thing. You really have to count very carefully,, you have to concentrate beyond mortal comprehension at times. You've got to make sure that all your facilities are working right. You may get into a counting routine: 1-2-3-4, 2-2-3-4, 3-2-2-4-, and so on. Much of the standard repertoire has cuse that you know. But you never know a piece until you have every mistake there is to make in it. This can happen in some of the oldies. You think you've counted and you'ved listened, perhaps a little bit more than you should have, and you've listened incorrectly. Sometimes listening is more fallible than counting."

Tuning the drums is one of the tougher bits of business. "You tune while the music is going on. The best time to do it is in the louder places." Put your head down next to the drum head and sure enough, you can hear the pitch change even while music is going on around you."The strategic point in the tuning of the instrument is to get the proper relationship all the way around the head. To make sure that 6 o'clock sounds like 12 o'clock."

Ask Begun what is difficult to play, and he will tell you instantly: "It's not some humongous display" -- with which he does a lightning sweep that carries his sticks across all four drums in a flash. "It's something like this," and he leans intently over the drum he calls No. 2 and begins to play so softly you can hardly hear the sound. "That's the opening of 'La Mer' by Debussy. The problem is to get the long, sustained sound -- it's on a B -- and keep it going absolutely pianissimo. That's hard."

"Something else that's hard we were just rehearsing: tghe Barber Violin Concerto that we're playing with Issac Stern. It's at the beginning of the finale.Barber is extraordinarily astute. He actually studied the instruments, which we wish more composers would do. He asks for mutes."

Mutes on tympani? Begun takes them out: small green felt pads about four inches around. He lays them on top of the drum heads and begins to play. The sound is immediately more muted, dryer. He plays triplets played on two drums and presto. Faster than any eye could follow, his sticks move through the intricate design required to play Barber's music at the proper speed.

"Isaac asked, in the rehearsal, for an accent on the first and third beats. That's hard," Begun says. But it does not seem so as he does it with the look of triumphant invincibility you see when Baryshnikov finishes a spectacular leap or Pavarotti flings out one of those top C's.

Begun began playing drums when he was a kid. But by the time he got to high school he realized that there was more to music than jazz. Not long after that he began his studies at the Juilliard School with Saul Goodman of the New York Philharmonic, the godfather of an entire generation of timpanists.

The next time you see Begun's head right down there on the mylar plastic he'll be tuning. And a few moments later there may be another of those great "humongous" explosions that cut through the whole orchestral fabric. And it will be on a new pitch that Begun found while all around him his colleagues were playing as loudly as they could.

And you will know from the look on his face and his imperious bearing that Fred Begun knows he is right on the mark -- as he has been for nearly three decades.