It's 0800 - eight o'clock in the morning if you're a civilian - a full 12 hours before some 3,000 guests are due to arrive at the Marine Barracks for the evening parade, but the troops are getting ready for them. The Marine Band and the Drum and Bugle Corps are on the parade deck - Marine speak for a manicured lawn slightly larger than a footbal field - warming up. While the bands play, the rest of the cast gathers in the wings - officers, the color guard, the rifle-toting silent drill team, marching men, and even a few marching women. When the music stops and the bands retreat, the deck is momentarily empty but the air is thick with anticipation. A formal reharsal is about to begin.

Master Sergeant David Ankram, known as the "brains of the parade," stands behind the leachers equipped with a head set and a walkie-talkie and calls the shots.

"Standing by to play the tape," says Ankram into his walkie-talkie.

At the signal, Corp. William Ortbals, narrator of the parade, flicks on a tape recorder and a voice, his own, booms: "Ladies and gentlemen, welcome to Marine Barracks Washington, D.C."

Ortbals stands next to the tape recorder, microphone in hand and ready to go live at any second in case the tape breaks.

"Standing by to cut the lights," says Ankram.

A Marine rings twice on a brass ship's bell on the flagpole and the light crew, on a platform high above the bleachers, goes through the motions of cutting the lights, although it's really shortly after nine in the morning. In the imagined darkness, a bugler blows the call to assemble and the Drum and Bugle Corps marches on behind Gunnery Sergeant Michael Patri, the drum major, who wields a mace twice as long as any high-school majorette's baton.

As the marital music fades, eight barracks officers, wearing everyday uniforms because this is only a rehearsal but dangling well-polished swords from scabbards, march across the field and then disappearl into the shadows of the arcade that lines the courtyard of the old brick barracks. In the arcade, which is sheathed in black canvas and hidden behind shrubs to make it a perfect backstage for a night-ime show, another Marine wearing a headset is in touch with Sergeant Ankram.

Ankram gives the cue for the ceremonial entry of Private First Class Chesty VI, and English blulldog who serves as the Marine mascot.

There is a slight delay - imperceptible to a civilian - because Chesty, named for Marine hero Chesty Puller, whom he said to resemble, has staged a lie-down strike.

"It's the humidity," explains Chesty's trainer, Gunner Sergeant Joseph Naradzay, sympathetically. "He likes the cold pavement and he wouldn't get up."

In seconds, however, Chesty, a nine-month-old puppy making his parade debut this season, is pulled to his feet and led onto the parade deck on a short leash. Sitting down on cue, Chesty pauses to receive the applause thatt will greet him at the real parade, whether or not be marched in as smartly as the parade brass would like. When the dog and his handlerr exit, a voice shouts "Sound Attention!" The cry is passed across the field and into the arcade, where it echoes and dwindles to cry unintelligible to civilians. The Marines march from their hiding places onto the field, their feet moving in synch and their left arms extended to the shoulders of the Marines next to them.

As they march, uniformed people in the audience are taking notes. They are not reporters, but critiquers, noting every misstep or unpolished shoe sole. As the color guard passes review, bearing both the U.S. flag and the Marine Corps flag with its 47 colored silk streamers - one for every campaign fought by Marines - the critiquers are scriblling furiously. As the nine members of the silent drill team twirl their rifles with split-second timing, the critiquers are sitill busy with their note pads.

Meanwhile, in the shadowy arcades lurk the supernumeraries, waiting in the wings for disaster to strike. Suppose someone drops a cover - that means hat - or a bayonet? A platoon sergeant will put a white-gloved hand behind his back, alerting the supers. Then, getting on okay from Sergeant Ankram via walkie-talkie, the super crouches low and, at a strategic moment when the lights are focused elsewhere, sneaks onto the field to repair the damage.

"Most of the time I bring people back who crash," says Lance Corporal Jerome Dukin, who later has an opportunity to demonstrate the technique. A Marine crashes during the rehearsal, falling back in a heap. Dukon carries his fallen comrade out, then acts as a stand-in. "If you push your knees back when you stand there, you cut off the circulation," says Dukon.

As the band stirs the crowd with "From the Halls of Montezuma," 175 Marines pass in review before their commanding officer. Lance Corporal Lucian Noble, watching from the arcade outside the Press Shop, pictures the troops as they will look tonight in the 175 dress uniforms he and a colleaguee have just pressed. "It's not so bad," he says nobly, but allows that he's glad his part in the parade his over.

But Corporal Gary Stahlhut's big role is just beginning. As the band plays the Navy Hymn - the Marines are part of the Navy - Stahlut, bugle in hand; mounts the stairs to the top floor of the barracks. He can hear the music, "Eternal Father, strong to save," as he climbs a ladder to an already-opened trap door in the roof. Stahlhut positions himself on the ramparts; on windy nights he braces himself inside a metal circle. As the hymn ends - "O hear us when we pray to theee, for those in peril on the sea" - a spotlight shines on the bugler, who breaks the silence and ends the parade with "Taps."

When rehearsal ends and the parade deck clears, the grounds crew attacks it wtih rakes.

"It's worse than a golf course - they all use the same tread," explains Buffy Gray, a civilian who recently received a degree in ornamental horticulture from Cornell and who, is in charge of the plantings and flowers around the Barracks as well as of plugging up holes in the parade deck. As the grounds crew makes the grass stand upright, the parade brass gather in an officer's lounge to dissect the rehearsal over coffee and chocolate-chip cookies.

Major John Admire, chief operations officer, has observed all. Somebody's sword almost covered his foot, and somebody else was leaning on his weapon. He talks about early sword drops and mis-spins of Rifles and even bad butts. (For the benefit of a civilian present it is explained that "bad butts" refers to the way a rifle handle hits the ground." But Admire ends on a happy note: There's zero percent chance of rain for tonight's parade.

"Whose forecast is that? Ripley's?" hoo a skeptic.

As the officers critique, the enlisted Marines are lining up outside the Barracle barber shop for their weekly head-shaving. The rest of the day will be "prep times time to get their shoes shined and their soles blackened and time to get some rest before the parade.

Private First Class Chesty VI is unwinding by playing basketball in the gym with some human Marines and with the retired mascot, Chesty V. Sergeant Naradzay, who takes both dogs home with him to Silver Spring every night, watches indulgently but he has some plans for Chesty VI for the afternoon.

"Our expertise is great for handling humans, but there is a communications gave with the dog," he laments. Young Chesty has been through recruit training; he's been to obedience school.But he still doesn't step smartly on the parade deck. This afternoon, after chow - which is given to Chesty at strategic times to set his biological clock so he doesn't ever foul the parade deck - Chesty will do extra drill. While the other Marines are resting or playing basketball, Chesty and his handler will be doing their thing on the parade deck.

C'mon, Chesty, how do you ever expect to make corporal?

TO THE COLORS

Evening Parades are held every Friday night throughout the summer at the Marine Barracks, Eighth and I Streets SE, beginning at 8:20. Admission is free. Reserved seats may be obtained up to three weeks in advance by calling 433-4681. Some seats are unreserved and are available on a first come, first-served basis to people entering the main gate after 7:30. The barracks are about three blocks from the Eastern Market Metro Station. Motorists may park at the Washington Navy Yard, Ninth and I Streets SE, and take free shuttle buses to and from the parade.

Marines also march in Sunset Parades at 7:30 every Tuesday June through August and the Marine Corps War Memorial (Iwo Jim a memorial). No reserved seats. Starting at 6:30 there's a free shuttle bus from the Arlington National Cemetery visitors center after the parade it'll take you back there.

Also on Tuesday at 7:30, the Army put on Torchlight Tattoos at the Jefferson Memorial. Arrive about 7 to get a seat on the steps.

And on Wednesdays at 8:40, the U.S. Navy Band, Sea Chanters and Ceremony Guard put on a show that combines forny parading with sea chanties and a sound-and-light demonstration at the Navy Yard. For free reservations, call 433-2218. CAPTION: Picture, THE UNITED STATES MARINE BAND AT AN EVENING PARADE. By Gerald Martineau.