Sandra Schwarz’s new violin is old, and her old instrument is new.

Schwarz owns a modern-style violin made in 1789, but the Baroque period instrument Schwarz plays with Iris Quartet for the Feb. 24 Housing Resources Board benefit was fabricated in the 1980s.

The two instruments appear similar to the unschooled eye, but Schwarz points to subtle distinctions.

“They took the Baroque instrument and basically did major surgery,” Schwarz said. “They grafted on a longer neck to get a bigger sound, and they tuned half-a-step higher. They raised the angle of the strings for more tension.”

Other changes were also geared to enlarging the sound, Schwarz says. A small post inside the violin that connects its top surface to its vibrating belly was lengthened, increasing the instrument’s resonance.

The changes were driven by history. In post-French-Revolution Europe, concerts for aristocrats in tiny venues were supplanted by music that had to project throughout a large hall.

“By 1830, the changes to the instruments were done,” Schwarz said. “The music changed, too, to bigger, grand works by composers like Dvorzak and Beethoven.”

That Romantic style was then applied by musicians to their performances of other, earlier music, Schwarz says.

It wasn’t until early 20th century that research of original music treatises in Holland, Germany and England reconstructed the authentic style of the Barque period – 1600-1750, a span that embraces Purcell, Telemann and Haydn.

Returning to musical sources meant reconstructing the period instru- ments.

Even the violin bow had to be reshaped.

The arch of the bows strings was restored from the concave shape of the contemporary bow to the convex Baroque bow.

“That modern bow keeps a more even sound,” Schwarz said. “The Baroque bow stroke is loudest at the frog (the bottom end of the bow); there’s always a decay because they were mimicking speech and song.”

The Baroque bow is held four inches from the end, Schwarz notes, while the modern bow is held much lower, at the tip of the frog.

The older grip gives the wrist more mobility and puts weight behind the hand, according to Schwarz, to produce the rapid string-crossing characteristic of the Baroque music – music for which the Iris Quartet is known world-wide.

The quartet features two Bainbridge Island residents: Schwarz on violin and Janet See on flute. The other members are Jillon Stoppels Dupree on harpsichord and Margriet Tindemans playing the viola da gamba.

Learning to play Baroque music the way it was composed to be performed has made Schwarz more appreciative of the period’s composers.

“Many times I had thought the Haydn quartets boring,” Schwarz said. “All of a sudden the music made sense to me. It was being played the way Haydn intended – not what some 19th century violinist thought it should sound like.”

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The Iris Quartet plays a concert of early music that includes works by Telemann, Rameau and Marais on period instruments to benefit the Housing Resources Board 3 p.m. Feb 24 at Rolling Bay Presbyterian Church.

Tickets are $25/adult; $15 seniors and students, available at Eagle Harbor Books, Vern’s Winslow Drugs, and the Housing Resources Board office. Call 842-1909 for more information.