Mandolinist Akira Otsuka grew up in Japan, listening to bluegrass and hating the Beatles. Guitarist Al Petteway grew up in Maryland and Virginia, playing rock and emulating the Beatles.

Today both are members of Grazz Matazz, a local quintet that last year garnered five Washington Area Music Association Award nominations and ultimately won a Wammie for Best Album in the acoustic category for 1984's "Delinquent Minor."

Did Otsuka finally succumb to rock? Or did Petteway discover the joy of bluegrass? As it happens, the answer to both questions is yes.

Thus, when Grazz Matazz performs at the Birchmere tonight, listeners are likely to hear an occasional bluegrass tune thrown in among acoustic rock versions of, say, something recorded by Little Feat, as well as a healthy dose of western swing and reggae.

"It's tough to describe," says Petteway of the band's sound. "We really mix things up. I think what probably makes us different from most groups is that we really like a lot of different kinds of styles, and we try to adapt each tune to acoustic music if it seems right."

Otsuka agrees. "We don't confine or limit ourselves musically," he explains, noting that his tastes have broadened considerably in the past decade.

But then, so have Petteway's. Raised on rock, Petteway turned to acoustic music in the late '70s after playing Top 40 tunes in the Washington area for several years. Once in the company of folk musicians, he soon discovered that there were other virtuoso guitarists besides his longtime favorite Doc Watson. He began listening to the recordings of Tony Rice and Dan Crary, among others.

"I was kind of sick of the whole Top 40 scene," says Petteway, 33. "So folk and bluegrass was really refreshing. I really enjoyed it because a whole new world opened up on the guitar that I hadn't even approached before. And the singing, too. I really got into singing the tenor parts."

Grazz Matazz grew out of a 1981 recording project that originally began as a kind of area all-star session. For a variety of reasons, the album wasn't released until 1984. By then Grazz Matazz had begun to perform at the Birchmere, minus a few of the people involved in the recording. (Besides Otsuka and Petteway, the band now includes Petteway's wife, Pat, on rhythm guitar and piano, fiddler Michael Stein and bassist Fred Smith.)

Petteway, who works for National Geographic magazine, recalls first seeing Otsuka perform with a popular area band called the Grass Menagerie in the late '70s. "I had heard him enough to know that he was probably the best mandolinist in the area by the time we started working on the album . . . We learned a lot from each other. He had never played a lot of funky rhythms, and he taught me a lot about bluegrass. We've sort of evolved together musically, teaching each other along the way."

For Otsuka, 37, Grazz Matazz is the culmination of a long musical odyssey that began when he was a teen-ager in Japan, listening to the bluegrass albums his older brother brought home from college. Otsuka started playing the mandolin at 16, teaching himself chord positions by watching musicians perform in concert or, incredibly, by examining how various mandolinists held their instruments on the front of album jackets.

"In Japan," Otsuka says, "we appreciate a lot of different music. Classical music is big there. Jazz. Hawaiian music and bluegrass, too. I became a bluegrass freak."

Otsuka's favorite band was the Country Gentlemen, which featured the spirited mandolin playing of John Duffey. (Now a member of the Seldom Scene, Duffey is one of Otsuka's biggest boosters.) By the time Otsuka first arrived in the States, touring with a Japanese band called Bluegrass 45 in 1971, he had already memorized every Duffey solo he could find on record. "I knew all the breaks better than he did," he says proudly.

Shortly after his arrival in the United States, Otsuka met Duffey and the two became fast friends. But first, Otsuka and the other members of Bluegrass 45 appeared at Indiana's Bean Blossom Festival along with the greatest names in Bluegrass.

"It was a dream come true," he says. "That was the first time I met Bill Monroe, Jimmy Martin, Jimmy Gaudreau . . . Tony Rice and Sam Bush. They were all standing around talking to each other and I just couldn't believe I was there, too."

In 1973, Otsuka came to the United States to stay and immediately landed a job playing with Cliff Waldron's band. He spent the '70s working with Waldron, Eddie Adcock and the Grass Menagerie, developing a taste for country rock and the percussive rhythms of Little Feat along the way. Now employed as a computer programmer for a local bank, Otsuka prefers playing music part-time. "The less you play," he says, "the more fun it is."

In addition to Grazz Matazz, Otsuka and Petteway have been busy with other musical projects. Not long ago Petteway recorded several tracks with David Grisman's band for a forthcoming album by Liz Meyers, and he and Otsuka work frequently with Peter Rowan when he's on the East Coast.

Moreover, Otsuka recently discovered that growing up in Japan has prepared him well for a variety of other assignments in bluegrass. Last October he accompanied the Seldom Scene on a brief tour of Japan. "I was their road manager, translator, tour guide and soundman," he says with a laugh.