The Bach Festival continues to explore and expose the roots of J.S. Bach's music.

For the next three weeks, Baroque music fans from around the world will celebrate the music and legacy of Johann Sebastian Bach. But while these fans at the Carmel Bach Festival eagerly await their annual fix, they might not be aware that the name of their favorite music was originally intended as a putdown: It meant "bizarre." That''s what enlightened critics of the later 18th century thought of the previous generation''s music and art.

Bach Festival regulars may find "bizarre" an appropriate description for some of the instruments making more frequent appearances with the orchestra in recent years. For instance, what are those strange, guitar-like things with long necks projecting above the players'' heads? Why does a man walk out on stage with an anemic-looking cello, play for one aria, and disappear backstage? Why are the violinists holding their bows the wrong way? Three words--Baroque performance practice--hold the answers to these and other questions.

Since Bruno Weil''s arrival as the music director of the Bach Festival in 1992, tempos have grown brisker, new artists, known for their early music expertise, replaced familiar ones, and long-forgotten Baroque instruments, used on an occasional basis in past Festivals, havebecome a more regular part of the Festival Orchestra.

These changes, once startling to Carmel audiences, are part of a much wider trend--the movement toward performing the music of the past according to the performance standards of its own time. In the case of Baroque music, this means playing 17th- and early 18th-century music in a historically informed manner.

The seeds of today''s early music revival were planted with Mendels-sohn''s 1829 performance of Bach''s St. Matthew Passion. In the past couple of decades it has become a veritable early music craze, as even punk rockers reach for CDs of Gregorian chant and Hildegard von Bingen. Cities like Berkeley, Seattle, Boston, New York, Amsterdam, and London host festivals and workshops for aspiring early music specialists. Instrument makers produce harpsichords, viols, recorders, and other early instruments based on careful study of museum specimens. The objective, ever dangling beyond reach, is to recreate as closely as possible the sound of the original performance. This means using appropriate instruments, playing them in the manner they were once played, and interpreting the music according to the conventions of the period.

Bach frequently employed specific instrumental colors to emphasize the mood of a particular aria in his sacred vocal works. This accounts for last year''s mysterious appearance and sudden disappearance of Bay Area musician John Dornenburg, holding what looked like a cello with sloping shoulders during the Passion performances. The instrument is a viola da gamba, or "leg viol," held by the legs rather than the arm of the performer, and a beautifully carved head replaces the decorative scroll of the modern instrument. Its plangent tone is perfectly suited to moments of intense sorrow or introspection--for instance, the heart-rending alto aria sung immediately after Jesus'' death in last year''s St. John Passion. Bach also called for viola da gamba in two arias from this year''s Sunday offering, the St. Matthew Passion. In one, the viola da gamba accompanies a tenor soloist responding to Jesus'' cross-examination by Pilate. In the other, it joins a bass soloist who identifies with Jesus as he drags his cross to Golgotha.

Particularly conspicuous in last year''s concerts were large lutes called theorbos. Their long necks give them a high profile, leading listeners to ask "What on earth is that?" The theorbo is a low-pitched lute used during the Baroque period to reinforce the bass line. In addition to six or seven pairs of gut strings of normal length, the theorbo has seven or eight very long strings requiring an extension of the instrument''s neck. The instrument produces a bright, clear sound, valuable for projecting low bass notes. Bach specifically indicated the use of theorbo in the St. John Passion, performed on last year''s Sunday programs. Three Baroque lutenists, Deborah Fox, Richard Kolb and Grant Herreid, were brought in from New York for the occasion and are returning this year as regular members of the Festival Orchestra.

This year''s Thursday night concert places another seldom-heard instrument in the spotlight: the viola d''amore ("love viol"). Similar in size to the modern viola, the viola d''amore has a wavy outline and curvaceous, flame-shaped sound holes. Like the viola da gamba, it terminates in an elegantly carved head. The instrument has two sets of strings--seven strings the player presses to the fingerboard to produce different pitches, and seven sympathetic strings running beneath the fingerboard. The strings set into motion by the bow cause the sympathetic strings to vibrate as well, producing a sweet, glowing sound almost guaranteed to rouse amorous feelings. Principal violist George Thomson will play a Vivaldi concerto for viola d''amore at the Thursday night concert.

The Vivaldi viola d''amore concerto is just one of the unusual offerings on the Thursday concert. Concertmaster Elizabeth Wallfisch will lead a select band of string players in performances of six Baroque concertos. The program ends with not one but two concertos for four violins. Like the rest of the program, these concertos will be performed on Baroque instruments.

Under Wallfisch''s leadership, the Thursday night program has become the most authentically Baroque event of the Festival. Each player who performs in this concert arrives in Carmel equipped with two instruments--a modern violin, viola or cello, and its Baroque equivalent. While they play their modern instrument in most of the concerts and recitals, they use only Baroque instruments (or modern replicas) for the Thursday evening concert. This affects both sonority and interpretation.

While the modern string instruments have wire strings, putting them under very high tension, the Baroque ones have gut strings or gut strings wound with metal wire. Instead of the vibrant A440 orchestras tune to today (a frequency of 440 cycles per second for the "A" above middle "C"), the Baroque instruments are tuned to a more relaxed A415. Their necks are shorter and are aligned with the body of the instrument. The modern instruments we''re accustomed to hearing replaced gut strings with wire or nylon strings, raised the bridge holding up the strings, lengthened the neck, angled the fingerboard back, and raised the pitch. Each of these innovations increased the tension on the strings to produce a more brilliant, penetrating sound--one designed to engage the attention of listeners in large concert halls. The performers in the Thursday concert use Baroque bows, which curve slightly outward and away from the hair, and grip them in the old way--closer to the center of the bow. This type of bow is lighter and more flexible than the modern bow, allowing the players to shape phrases with lightness and delicacy.

It''s easy to assume that the development of newer, better instruments led to the extinction of older, more "primitive" ones. Such is the often unrecognized influence of Darwin''s evolutionary theory on our thinking. While it''s true that the older instruments have nowhere near the power and brilliance of modern instruments, musicians who have devoted themselves to the study of Baroque performance practice have discovered that the old instruments have their own advantages. With period instruments, they can negotiate rapid scales and arpeggios with remarkable agility and panache. They can also render more tender passages with the utmost delicacy and sensitivity to nuance. Their music-making evokes the sounds of an age when people took time to listen to music rather than using it as a backdrop for more important things.

The upcoming Bach Festival programs give us an opportunity to turn off our beepers and cell phones, forget about our Palm Pilots and to-do lists, and drink in the sounds of the Baroque era.

For a schedule of Carmel Bach Festival events, visit www.bachfestival.org