Sitting out there in the audience, I am more inclined to empathize with a violinist who is playing one of Bach's unaccompanied sonatas or partitas than with any other kind of musician. Nothing in the world of music is more solitary than such an artist, out on a bare stage without even a piano for moral and harmonic support, and to make it even more daunting he is tackling one of the most challenging assignments in the performing arts.

There are other works for an unaccompanied string instrument -- Paganini's violin caprices, for example, and Bach's cello suites -- but they're not quite in the same class. The Paganini music is flashy, crowd-pleasing stuff; the Bach cello pieces are great music (perhaps a shade below the violin works) and technically formidable, but the cellist has a more resourceful instrument at his disposal and its sheer size and power make him seem somehow less fragile, less alone.

The problems in Bach's unaccompanied violin music are of two kinds. First, it was written for an instrument subtly different from the modern violin -- and that term includes practically every existing instrument by Stradivari, which have been "modernized" in the last century or so. The baroque violin's gut strings and slightly lower pitch produced warmth more readily than the brilliance we expect from the wire-strung, high-tuned instruments of today.Its bridge was less curved, making it easier for the violinist to play notes on two or more strings simultaneously, and the baroque bow, with its lower tension and softer attack, produced an effect more natural and attractive in this kind of music than the slightly feverish scramblings and scrapings that are taken for granted in modern performances.

The other problem is less concrete yet more simply stated: This is great music --lyric, thoughtful and intricately structured --often treated as an occasion for the display of gee-whiz technique. Many performers show little inclination (or, one sometimes suspects, ability) to probe the underlying structures, which range from dance melodies to fugues of great complexity (including, of course, one chaconne that is among the creative spirit's noblest monuments). Technique is a fine thing in its place, but when it becomes an end in itself, at the expense of musical interpretation, it stands as a barrier between the composer and the listener.

These problems are squarely faced and satisfactorily answered in two recently issued collections that present the complete Bach sonatas and partitas for unaccompanied violin on low-priced labels. Neither Sergiu Luca on Nonesuch (HC-73030, three records) nor Joseph Szigeti in the Vanguard reissue of his classic recording (HM 54/55/56, three records), has quite the technique displayed by Milstein (on Deutsche Grammophon) or Grumiaux (whose Philips recording is, to my taste, the most musically satisfying exemplar of the modern virtuoso approach). But technique is emphatically not what this music is all about.

Luca, who performed this music live here a few seasons ago, uses a baroque violin and bow in something approaching their original condition, and for the first time since seeing his live performance, I hear the music sounding sweet, natural and unforced -- in a word, musical: the kind of thing you can imagine a musician playing for his own and his audience's enjoyment, not merely for instruction or as a tour de force. He makes it sound almost easy, whereas other players (or, rather, their instruments) often make it sound agonizingly difficult. And that's not what the music is all about, either. Anyone who is interested in these pieces as music, not simply as a series of mountains to be scaled, should be familiar with Luca's interpretation.

On the other hand, anyone interested in these pieces as music and as a series of mountains to be scaled should be familiar with Szigeti's interpretation. It shares the difficulties of virtuoso performances on the modern instrument, and it does not offer the usual compensations; Szigeti's technique is good but not dazzling, and his pitch is sometimes a bit off-center. But whatever its shortcomings, this remains the most eloquent statement on records of what the music is about and how its parts work together. Luca is preferable for pure enjoyment and his interpretation is technically a lot more authentic, but Szigeti remains unique. I have kept his performance within easy reach ever since it was first issued, and it will retain that place of honor. But Luca's will take a spot right beside it.