Band leader Keith Brion is a John Philip Sousa junkie. He can rattle off all sorts of Sousa trivia. He has a Sousa Band of more than 130 rotating members, whom he has sit in the "Sousa formation" to play Sousa marches. For 10 years now, he's been conducting Sousa programs for major orchestras, such as the National Symphony Orchestra tonight and tomorrow night at the Kennedy Center Concert Hall, dressed as Sousa.

He has Sousa's mannerisms down pat, including that ever-so-famous two-arms-swinging motion that became synonymous with the late-19th-century conductor-composer.

He even used a Sousa baton to coax the marches out of the musicians -- until tragedy struck.

"Somebody brought me one of Sousa's original batons when we were performing at Carnegie Hall," Brion says, "and as soon as I walked out onstage, I noticed it had a big crack in it. And I thought, if I break Sousa's baton in the middle of this concert, that'll be it. I'm not superstitious, but it seemed like a terrible jinx."

But make no mistake, Brion is not some Sousa copycat. He is a Sousa emulator.

And why has this genial New Englander decided to spend a large part of his life acting like one of the most famous composers born and bred in Washington?

"I was dumbfounded when we did the concert the first time by how happy people were in the audience," he recalls of his first Sousa concert 12 years ago. "I had spent 25 years conducting and had never done anything that made people so happy. It felt good to see people smiling." Plus, he says, the Sousa repertoire is "inexhaustible." Besides the 15 operas and dozens of classical pieces Sousa composed, "there are 135 Sousa marches," says Brion. "I could do six new ones for each concert forever and ever and not get close to the bottom. And they are such high quality, the marches. The more I study them, the more excited I get."

Brion's Sousa reincarnation began in 1978 at Yale. Brion, the university's band director, was reading Paul E. Bierley's Sousa biography and came across an anecdote about a Sousa concert at Yale nearly a hundred years ago.

"Sousa was walking across the stage when he was struck with a bout of malaria," says Brion. "It's not clear whether he contracted that in New Haven or in Washington -- that was in the days when Washington was still mostly swamp."

He sits back and chuckles. Brion has the presence of a friendly college music professor: a comfortable manner, a navy blue knit vest, grayish, thinning hair and a mustache. You can tell he likes to tell stories.

It was the Yale episode in the book, he says, that got him to thinking. "I got this funny idea, 'Well, how about if we use the concert band disguised as Sousa's band,' " he says, pulling at his bushy left eyebrow. " 'Instead of doing a tribute to him, we should become like a time machine.'

"Then my son's roommate had a girlfriend who did makeup, and she kept saying, 'Well you're going to dress up like Sousa, aren't you?' I said, 'Well, I'll wear the uniform, but I'm not going to look like Sousa.' " This was before he turned Sousa Gray.

"Well," he says, laughing, "they talked me into it."

He found an old lieutenant commander's wool uniform that had been left at a New Haven dry cleaners after World War II -- "and it fit!" he declares. He had some copies made of Sousa's medals. Donned a sword, wire-frame glasses and white gloves -- just like Sousa. Powdered, parted and slicked back his hair.

"I'll never forget going through the stage door," he says of his first performance at Yale. "I had this strange feeling that I was going into another dimension. It was like science fiction almost. It really was odd."

Over the years, there have been a few changes, a few updates. He got rid of that 40-year-old thick wool uniform. "I wore it for the first three years," he says, "but I was always passing out -- especially in the summertime." He now wears a tropical-weight suit -- black wool gabardine with 35 yards of black braid -- a copy of Sousa's civilian uniform.

He dropped the kid gloves in favor of fabric ones with rubber fingertips so he can get a better grip on the pages of the scores. ("Sousa had trouble turning pages with the kid gloves," says Brion, "so he had little corners put on the pages so he could get ahold of them.")

And he's added some classical pieces of that era to his repertoire, so it's not strictly Sousa, but rather a survey of light music. And he's eased up his Sousa mannerisms a little bit -- thanks to a piece of advice.

"In 1986, John Philip Sousa III and I had breakfast together," says Brion. "I had spent six years getting it down, the routine. I got it from newspaper accounts and from what people said they remembered and kept merging it all together and doing it. And he said, 'You know, you've got this thing down.' I said, 'Thanks.'

"And then he said: 'Maybe it's time you start being yourself a bit too.' "