When Christian Tetzlaff launches into Johann Sebastian Bach's Sonatas and Partitas for Unaccompanied Violin on April 29 at New York's Alice Tully Hall, he will be ascending the Mount Everest of the violin repertoire.

Most violinists, if they are lucky enough to get through this music unscathed, make it sound like music beaten into submission — beautiful, yes, but labored, tortured, driven up to and then beyond the edge of the instrument's powers.

In Tetzlaff's hands, these strange, ascetic works sound like music written for the violin, an instrument Bach played brilliantly, even though he is better-known as a keyboard player.

"Playing them all at once is very difficult, because the music asks so much of the player," Tetzlaff said recently from his home in Hamburg, Germany.

"The six works should be played all on the same occasion, for the same audience, because they have a certain continuity," he said. "I used to divide the performance over two evenings, but that doesn't work because you do not have the same audience for both segments.

"In New York, I will play the complete set in one evening with a long interval; the first part from 5 [p.m.] to 7 [p.m.], the second from 8 [p.m.] to 10 [p.m.]."

Striking Differences

There is a natural division in the music; the first four works are in minor keys and the last two are in major keys.

Although they all are written for unaccompanied violin and use daunting chords and counterpoint, the six works on Tetzlaff's program include two strikingly different kinds of music.

The three Partitas are dance suites in the French baroque style, less suited to deep meditation and intimate emotion than the three Sonatas, which are written in the more serious Italian Sonata da chiesa (Church sonata) form. This gives more opportunity for serious reflection.

All three Sonatas begin with a thoughtful slow movement, marked Adagio or Grave and followed by a fugue and another slow movement before reaching a faster-paced finale.

In these church sonatas, Tetzlaff said, Bach implanted religious themes, evoking three different feasts of the Christian liturgical year: Christmas in Sonata No. 1, Good Friday in No. 2 and Pentecost in No. 3. The Partitas are concerned with the daily life of ordinary people — a dance of life. But the greatest and best-known movement of them all, the massive Chaconne that ends Partita No. 2 in B minor, could be described as a dance of death.

Bach approached this subject with mixed emotions — the pain of loss and the consoling idea that death was the beginning of a new life.

At 13 minutes on Tetzlaff's recording of the works, the Chaconne is by far the longest movement, and many music lovers consider it the greatest work ever composed for solo violin,

"It is a requiem for Bach's [first wife, Maria Barbara] written in the year she died and containing allusions to many Lutheran chorales that deal with death," Tetzlaff said.

Symbolic elements have always been evident in Bach's vocal music, where there is a text that clarifies the melodic symbolism — the sound of the Wise Men's procession en route to Bethlehem, for example, in his Cantata 45.

In purely instrumental music, it is not so simple to uncover the symbols. But in the traditional Lutheran chorales, which were a cornerstone of Bach's musical thinking, words and music are closely linked; a particular chorale melody, played on an instrument, would immediately bring certain words to the mind of a devout Lutheran in Bach's time, just as a few notes of "Happy Birthday to You" played on a piano at a typical 20th-century American gathering does.

The use of bits of chorale melody in the three Sonatas give the clue to their seasonal associations — Christmas chorales in No. 1, Passion chorales in No. 2 and Pentecost in No. 3.

The chorales relating to death in the great Chaconne would imply both grief and consolation, but Tetzlaff believes that the final resolution of the grief in the Chaconne comes only in the first movement of the next work in the cycle, the opening Adagio of the Sonata No. 3 in C. "It is not necessary for the listener to recognize the quotations and references or to interpret the symbols precisely," Tetzlaff said, "as long as the underlying emotion comes across. You experience the depth of the Chaconne if you think of death and other kinds of loss, and if you think of consolation."

Tetzlaff's Upbringing Similar To Bach's

He has gained a reputation as an intellectual player with extraordinary technique. Referring to Tetzlaff's performance of the Chaconne, The Washington Post's Thomas May wrote: "While a lesser artist would focus on Bach's awesome technical demands, for Tetzlaff they were merely the means by which he achieves overwhelming pathos and dramatic depth without obscuring the piece's logical design."

The chorale melodies are a part of Tetzlaff's childhood memories, and his performance reflects special awareness and sensitivity. Today he is not a member of any church, but his father was a Lutheran minister and a music lover whose four children all mastered at least one musical instrument and went on to become professional musicians. It was an environment not unlike that of Bach's own family. Ironically, he initially attracted international attention in 1988 with performances of Arnold Schoenberg's Violin Concerto, a work that is seldom heard and one that presents serious difficulties for the performer and the audience.

By the time he returned to New York in 1993, a New York Times headline said his career was "rooted in Schoenberg." He performs a wide range of music, from modern works by such composers as Alban Berg, Leos Janacek and Gyorgy Ligeti, to the neglected Violin Concerto of Robert Schumann.

The eight CDs he has recorded for Virgin cover a wide spectrum of composers, including Bach, Kurt Weill, Haydn, Mozart, Dvorak, Debussy and Lalo. Tetzlaff's future recording plans (on Virgin's parent label, EMI) include works by Bartok and Brahms.