Bach the way Bach heard it. They make 'em like they used to. Craftsmen from around the world are fashioning exquisite reproductions of early instruments, recreating tones and timbres that haven't been heard for centuries

FRITZ HELLER spares no effort in making an ``authentic'' set of Renaissance bagpipes. At his home in a small village in Belgium he raises the goats whose skin he uses for the bags. He gets woods from local fruit trees for the smaller pipes, and for the long ones, two-foot-long cows' horns imported from India. Since he has no model to work from - the originals of what was ``Europe's most important instrument'' have long since disappeared - he studies Renaissance paintings and writings to re-create the pipes.

In performance in Boston recently, the instrument - in duet with a shawm, a Renaissance wind instrument that looks like a clarinet - recreated the rhythms and pulses of a peasant folk dance.

Mr. Heller recently joined craftsmen from as far away as New Zealand, Japan, Europe, and England to exhibit their reproductions of historic instruments in conjunction with Boston's Seventh Annual Early Music Festival. These artisans re-create music of the past, from the 15th to the 18th centuries. Their beautifully crafted instruments come in every size and shape, with sundry, peculiar names; the sounds are strange to our ears - high and piercing, low and raspy, or soft and mellow.

They are the sounds of weddings and festivals from all over Europe and England - neither ``popular'' nor ``classic,'' professional or amateur, in the strict sense, because those distinctions didn't become rigid until the rather recent development of the concert hall.

The quality of workmanship in these reproductions is striking. Joe Baker of Hunger Mountain Instruments, in the Berkshires of Massachusetts, begins with wood from his own sugar-maple trees to carve his Hardingfele, or Norwegian folk fiddle. Then he decorates it with floral patterns traced in India ink, and inlays of abalone, ivory, and mother-of-pearl from Africa.

In addition to the usual four strings across the board, the Hardingfele has five sympathetic strings underneath, and nine pins for tuning. Popular in Norwegian villages as far back as three centuries ago, the uniquely constructed instrument allowed a town's single musician to make as much noise as possible at weddings, funerals, and dances.

Each player would tune his fiddle to his personal taste; different areas developed their own patterns of floral decorations, borders, and the unique carved dragon's head on the neck.

Mr. Baker stresses that fashioning an instrument is more than a craft - the maker must also understand acoustics and the unique musical properties of the instrument.

``I love starting with raw wood and ending with something that looks pretty and sounds beautiful,'' he says.

IN the unlikely setting of a converted chicken house, Stephen Sorli of Carlisle, Mass., makes his harpsichords using richly grained woods such as basswood, spotted beech, and acacia-burl to approximate the marbling of the originals. Mr. Sorli turns out three to six instruments a year: from a $3,000 model with a single manual or keyboard for students and amateurs to a $15,000 reproduction of a Flemish double-stop (two keyboards) with handsome block-printed designs.

Paul Irvin of Glenview, Ill., builds a $3,000 cherrywood clavichord, the small, portable keyboard instrument loved by Bach because of its expressive sound. Carl Fudge of Winchester, Mass., exhibited his beautifully decorated Flemish muselar virginal, one of the most popular keyboard instruments for home use.

Another common instrument of the home was the viol, an ancestor of the violin, held in front of the player, something like today's cello. Michael Plant of Sheffield, England, who makes reproductions of 17th-century viols, says they were mainly used by amateur musicians.

THESE are instruments to be played and heard, not set in a display case; and a highlight of the festival was a demonstration of the baroque violin by virtuosi Stanley Richie and Daniel Stepner, assisted by Elizabeth Wright on harpsichord and Laura Jeppesen on viola da gamba.

Working from original scores of 17th-century composer Salome Rossi Hebreo that are essentially no more than a sketch - notes without bar lines, slurs, or dynamic markings - the musicians engaged in a dialogue that had all the earmarks of theater: dancing, singing, speaking, chasing one another, with keyboard and gamba filling in background colors. The spontaneity of the performance and the special treat of hearing music as it once was played were reminders of the ageless continuity of rhythm and song.

See related article on Page 26.

Harpsichord reawakened

WITH the beginning of the 19th century, the harpsichord, Europe's principal keyboard instrument for the past 200 years, met its demise. The piano was ``today's child''; the harpsichord, a tinny-sounding antiquarian.

One of the victims of that obsolescence was a gorgeously decorated harpsichord made by Henri Hemsch in Paris in 1746, now in the collection of the Boston Museum of Fine Arts.

By 1888, when the museum set out to restore the Hemsch, harpsichord-making was a lost art, and the craftsmen worked in a vacuum of understanding. Nearly 100 years later, in 1981, D. Samuel Quigley, keeper of musical instruments at the museum, enlisted a team of experts to restore the Hemsch to ``its venerable age and sound'' - as close an approximation to the original look and sound as possible.

HARPSICHORD-MAKERS Allen Winkler of Boston and John Koster of New Bedford, Mass., scrupulously replaced the keyboards and jacks, or ``hammers,'' following what is known about Hemsch's techniques in harpsichord-making from recent scholarship.

Eighty-four soundboard cracks were repaired, and Sheridan Germann, a Smithsonian Institution assistant, undertook the enormous task of removing the old varnish, a painstaking endeavor using Q-tips and taking about 224 hours to uncover the painted decorations that decorate the entire surface of the instrument.

Like her colleagues, Ms. Germann worked to restore the Hemsch's brilliant color and original design without destroying a valuable historic artifact. That meant repainting only where necessary, and in a style that could not be distinguished from the original. ``We have something beautiful to the eye,'' she says. ``It should be kept, yet remain true to the spirit of the instrument.''

That's what the audience saw, with gasps of delight, when the Hemsch was recently unveiled in the museum's Remis Auditorium. But a musical instrument is not a painting, and in the hushed stillness of the auditorium the Hemsch was finally ``resurrected'' in a performance of Rameau and Bach by keyboardist John Gibbons.

A common figure in harpsichord paintings was a dead tree stump with a bird perched on it, symbolizing the dead wood that ``in life was silent but in death sings.'' Certainly, Mr. Gibbons's performance on his ``old friend'' was the perfect realization of that adage, as he explored the tonal and expressive potential of the instrument to its fullest.

This was not early music - it was timeless.

Because of an editing error, a story on Page 19 of yesterday's Monitor incorrectly implied that Boston's Museum of Fine Arts did a poor restoration of a Hemsch harpsichord in 1888. In fact, the museum did not acquire the harpischord until later, and has completed a thorough and exacting restoration to correct previous errors.