At the word "authentic," even the most devoted music lover is apt to go rigid with visions of lifeless, arcane concerts.

Out in the Midwest, however, a fresh Baroque wind has risen to blow the dust off gamba and harpsichord. It arrives here at 8 tonight when Ars Musica of Ann Arbor, Mich., breezes into Georgetown University's Gaston Hall for the first of a three-concert series -- on original instruments -- devoted to music of the 17th and 18th centuries.

A few minutes conversation with founder-director Lyndon Lawless reveals that this 13 member Baroque orchestra is authentically different.

"Our ultimate aim is not to recreate an 18th-century practices. And even if we could do it, it's not musically valid to transpose from one culture to another." Instead, he says, the group is concerned with whether a piece "works musically."

That common sense conbined with dedicated work over the nine years of its existence has helped Ars Musica generate what one newspaper called "an exquisite Baroque high" among its audiences in Ann Arbor and Detroit. But no ensemble can survive on Midwestern love alone. Hence, the obligatory New York debut at the 92nd Street "Y" later this week with an eye to garnering the recognition and reviews that lead to wider bookings and more recordings.

Though tonight's concert initiates the group's first Washington series, its debut here took place two years ago at the Smithsonian.

According to Lawless, audiences are drawn to Baroque music on original instruments because they "are looking for something new but they can't stand the really new. This is exactly what they want. The music is fresh, yet it's very accessible and these instruments are very colorful. They have such a variety of sound compared to modern instruments."

Modern, in Baroque terms, means the early 19th century, when halls got bigger and instruments were modified for greater tone projection. For example, the Baroque violin has a shorter, thicker neck set at a straighter angle to the body than its modern counterpart and uses thicker, pure gut strings rather than today's thin steel strings. Played with a lighter, outward curving bow, it sounds quieter and more transparent than the modern violin.

Baroque woodwinds are more sharply differentiated in color and do not have the modern devices that make fingering easy. Their uneven tone sometimes surprises today's audiences, but Baroque composers liked and exploited their light and dark sounds.

Dealing with Baroque music means "retuning your ears," says Penny Crawford, harpsichordist for Ars Musica. "The results are very different from what I grew up thinking of as musical." In the past, whatever the period, I would strive before all else to play with a long, beautiful, singing line -- a 19th century approach.Now I divide things into much smaller units and think about the little amounts of space between notes."

"It's like an arch," adds Lawless, stressing the Baroque emphasis on continual variation within a small scale. "Nineteenth-century composers thought about the sweep of the arch while Baroque musicians thought more about the stones in the arch."

The appeal of Baroque music is "part of a reaction against the enormity of modern life, part of that feeling people have of wanting to return to something simpler, more laid back," says violinist Alison Bury who joined Ars Musica a year ago.

"It's a comparatively new field and there's lots of scope for one's own giving it a freshness that comes from us."

Bury, who is English by birth, met her husband Richard Earle, an oboist with Ars Musica, in Salzburg where they had both come to study with Nikolaus Harnoncourt. Harnoncourt's Concentus Musicus Vienna was the grandfather of Baroque orchestras using original instruments and a direct model for Ars Musica. Like several other members of Ars Musica who have studied abroad, Bury and her husband were drawn to Ann Arbor by the opportunity to concentrate exclusively on Baroque music.

Lawless chose Ann Arbor for the groups's home both because he was there and he felt it had the money and cultural awareness that Ars Musica needed to develop. Despite difficult times (when some members resorted to selling television sets and working in restaurants to support their Baroque habit) the ensemble has survived. With the exception of Boston's Banchetto Musicale, this country has no other resident Baroque ensemble whose members make performance on original instruments the focus of their life.

Though the budget has risen from $1,000 in 1970 to $150,000 this season, the players still must supplement their income with outside efforts.

As Lawless says, the musicians of Ars Musica delve into the past but their aim remains that of the musicians in any era -- communication with an audience. "We make no claims of 'authenticity.' In the final analysis, we must satisfy our own musical consciences which are very much of the 20th century."