"I HAVE this terrible writer's block," says budding novelist Bonnie Merz. "'Annie has four violins and two cellos; 'Evita' will be running here for six months with five violins and three cellos. How am I supposed to get my book written when they do this to me?"

Bonnie Merz is a viola player who works in the pit orchestras at the Kennedy Center and the National Theatre. She has been writing a novel during the parts of musical shows when the violas are not playing, and the novel is bogged down because no violas are being used in musicals currently playing in Washington. She has trouble writing when she is not employed as a violist because she is busy doing home renovations. And she can't really write much during classical opera and ballet, because those composers keep the violas too busy.

Her spare-time activity in the pit is part of a tradition that goes back at least to the mid-19th century. In his "Evenings with the Orchestra," published then, Hector Berlioz describes an opera orchestra whose members "spend their time reading books -- or even discussing matters literary and musical" during their working hours. One of his acquaintances, he said, "during the first 15 performances of a well-known opera, read, re-read, pondered and mastered the three volumes of Humboldt's 'Cosmos.' Another, during the long run of a silly score now forgotten, managed to learn English; while a third, thanks to his exceptional memory, retailed to his neighbors the substance of some 10 volumes of tales, romances, anecdotes and risque stories."

Nobody was reading Humboldt's "Cosmos" on a recent evening in the pit of the Kennedy Center Opera House, where "Annie" is currently playing to standing-room audiences, but guitarist Fred Karns was reading "Sartre on Theater" right under the eyes of conductor Glen Clugston, who was toally unconcerned -- as long as Karns was ready for his cues. At a far end of the pit, trombonist Edward Kiehl was reading a study score of Mahler's 10th Symphony. "I can't play a record in the pit," he says, "so I just read the music and hear it in mind. I have to have something to occupy my mind, or I'd go nuts."

Playing the same music eight times a week for six weeks gives a musician a kind of economic security -- particularly in the Kennedy Center Orchestra, which has been tenured since going on strike and working out a new contract three years ago. But it can become deja vu after a while, and even in a show like "Annie," which has only a three stretches of five or 10 minutes without music, there were quite a few books and magazines next to the scores on the music stands. No newspapers or portable radios or television sets were in sight -- perhaps because there was a reporter sitting in the pit, or perhaps because, as Bonnie Merz puts it, "they're not a very colorful bunch at the Opera House. It's much more lively at the National."

She says she has been battery-operated television sets there, with the sound turned off, naturally -- particularly at Superbowl time or during a World Series, and portable radios with little earplugs. "I remember once," she says, "during an intermission or after a performance, I saw a member of the audience leaning over into the pit and I wondered why he was so interested in the pit orchestra. He wasn't; he was just trying to find out the latest baseball scores."

From the auditorium, only the back of the conductor's head can be seen, and occasionally a flick of his baton or his left hand giving a cue to one section of the orchestra. Behind the wall that separates pit from auditorium, far below the sight lines and the level of the stage, 20 players are spread the full width of the stage -- from a keyboard player on the audience's left, with a piano and two electronic instruments, to a percussionist at far right.

Between these extremes, from left to right, sit the strings, reeds and brass, each with a music stand and a little light glowing in the darkened hall. From time to time, when rests in the music permit, one or two members of the orchestra may drift over to the wall separating them from the audience and look up at the stage for a few free moments. From down there, it is possible to see the adult actors, more difficult to see the children. In "Annie," this sometimes means that only part of the show really makes sense from the pit.

Extracurricular pit activity used to be a serious problem, according to music director Clugston: "When I began conducting back in the '60s, you would see card games going on and players folding and unfolding newspapers, which can be very distracting to the audience. Sometimes I had to get tough, but not with an orchestra like this. These are better players -- more disciplined, and they seem to enjoy working together. Not that they just sit there counting their rests. Some of them are very good cartoonists; you can see their work in the scores. And they write little messages to each other, telling what they think of the music or suggesting new titles for a piece."

In pit activity, as in so many things, New York is apparently busier and less restrained than Washington. Harry Cykman, a free-lance New York violinist, has just become incorporated as Grandmaster Productions Inc., and is about to begin manufacturing an "International Grandmaster" pocket chess in New York orchestra pits.

Pit stories abound among the New York freelance musicians -- for example, the story of the barefoot cellist. It seems there was a cellist in the New york City Opera orchestra who took his shoes off while playing -- why not, since he found it more comfortable and nobody could see his feet down in the pit? One evening, he saw the conductor glaring toward the cello section, thought (erroneously) that the glare was meant for him, silently mouthed an obscenity at the conductor and stalked out of the pit in the middle of the first act. He spoiled his grand exit by forgetting his shoes. He had to go back and get them at intermission.

While few go barefoot, many New York pit musicians who wear tuxedo tops are less formal from the waist down, according to violinist Elliott Siegel of the Kennedy Center Orchestra. " In New York," he says, "I've seen guys in the pit wearing tuxedo tops with blue jeans and sneakers," he says. "Gene and I do not allow this kind of thing." "Gene" is violinist Eugene Dreyer, who contracts musicians for musical shows, while Siegel contracts for classical opera and ballet, at the Kennedy Center and Wolf Trap. Although the Opera House orchesta, whose nucleus first got together in the National Gallery Orchestra, is not a stable, permanent organization, there is still considerable free-lance activity available -- in the Terrace Theater, for example, which does not have its own orchestra. First choice for the Terrace is normally give to members of the Opera House orchestra, but there are usually conflicts -- ballet in the Opera House in December, for example, while operas are being given in the Terrace. There is a pool of about 60 players from whom the Opera House orchestra draws regularly, depending on the needs of a particular opera, and Sigel says he knows "60 or 75 more very talented players in Washington on whom I can call when several things are going on at once." The instrumental needs of opera and ballet are generally larger than those of musicals. For musicals in the Opera House, the orchestra contract requires a minimum of 20 players, and the number sometimes goes up to 26 or more. But Broadway shows are a cost-conscious operation, and the orchestrators are skilled at getting the maximum effect from the available resources. Maybe that's why you don't hear violas very much any more; they can get more volume out of a saxaphone, with a player who can also double on clairnet, flute and perhaps oboe.

Strings are needed for a particular kind of sound -- tender moments, for example, which seem to be getting less frequent in Broadway musicals. "Normally," as Eugene Dreyer explains, "you need more than one string to play the same part, and you more or less have to have violins and cellos. But the last three shows here come in without violas. I hope that's not becoming standard paractice." When the latest production of "Hello, Dolly" left New York, according to reports in freelance circles there, the string section was reduced to a single cello. "I don't know what they did to fell in the sound," says a New York musician. "Maybe a synthesizer?" dThere is reportedly a new production of "Pirates of Penzance" that replaces the whole string section with a synthesizer.

One hard-working reed player in "Annie" is Art Dawkins, who is playing alto and baritone saxophone as well as clarinet and flute -- with an extra percentage in his weekly paycheck for each added instrument. Like all four members of the reed section, he keeps his instruments neatly arrayed on racks next to his music stand. Sometimes, when he will have to make a very quick change from one instrument to another, he holds one in his lap while playing the other. "In extended numbers, like a dance," he says, "sometimes you will have to play something on each of those instruments." Like cellist Robert Newkirk, who teaches at Catholic University and plays in the Catholic University Trio, Dawkins divides his time between the pit and academic life, directing lthe jazz studies program at Howard University.

Newkirk has been playing for opera and ballet for years but is in his first season with musical shows "partly for economic reasons," he says. Dawkins browses a magazine during the relatively rare moments when he is not performing. "I an seldom in a position where I can watch a show," he says, "and I guess they don't interest me very much. In the 12 to 15 years I have been working in the pits, I think I have sat in the audience for only two or three shows. And hearing them down in the pit, from a position where I can't see anything, I've learned to appreciate how a blind person feels; we hear all this dialouge and imagine what it looks like."

Newkirk's attitude is different, perhaps because he is still new in the pit or perhaps because one cello doesn't keep you as busy in a musical as two saxes, a clairnet and a flute. "Occasionally," he says, "I try to sneak over to the side and try to look, but I can't do much of that. I do try to listen. If something interesting is happening, it slows down the inevitable boredom process. The biggest problem in a musical running three to six weeks is to keep your concentration going all the time."

In opera, most members of the orchestra are kept to busy to be bored. "I remember," says one player with long operatic experience, "somebody gave me a piece of candy once during 'Meistersinger' and it took me 45 minutes before I could open it."