Alexander Schneider the conductor -- as opposed to Schneider the violinist and Schneider the sage -- specializes in the elegant, rational musical language of the 18th century.

This is music -- Bach, Haydn, Mozart or whatever -- in which the current rage is to return to instruments of the times, gut strings, shorter bows in an effort to reproduce the exact sonorities that those composers may have heard. Schneider developed in an era when such niceties seemed of little consequence, when keyboard Bach belonged on a piano and Mozart symphonies sounded right on modern strings, with their bright, incisive sounds.

Maybe the time will come when Schneider's kind of sound, as displayed at his Brandenburg Ensemble's concert last night at the Kennedy Center's Terrace Theater, may be as much of an anachronism as period-performance once was, but not as long as he is around.

Whatever the merits of the instrumentation, Schneider would argue that such influences would never matter as much anyway as grace and intensity in phrasing, which were present aplenty last night in the program of Haydn, Bach and Mozart.

When you hear, for instance, the Bach Brandenburg Concerto No. 3 in G -- with its dark, fervent string themes -- that is played with the ardor and tonal luster that Schneider's mostly young musicians brought to this great work last night, stylistic matters become strictly secondary. This is music of considerable force. Last night the final movement was the whirlwind it should be, and the earlier movement was a little drama. Intonation, the bane of original instruments, was utterly secure. And in general, the performance was a joy.

Another pleasure of the evening was the performance of Haydn's Symphony No. 57 in D. Just having this little-known gem on the program was a delight. But there was also Schneider's relaxed, jaunty phrasing -- the same sort of intuitive grasp of Haydn's musical language that one relished years ago when the Schneider String Quartet was working its way toward a complete set of the Haydn quartets. This symphony is full of wit, with a wonderfully swaggering minuet and a madcap finale that anticipates the zany finale of the 88th symphony.

There are dozens of such works among the Haydn symphonies. The Kennedy Center should do a festival of them, with Schneider sharing responsibilities with that other master of Haydn, Antal Dorati.

There was also a warm, gracious version of that wonderful expression of mellow elegance, Mozart's Symphony No. 29 in A. What other composer could write an opening movement of such depth on basically two notes, as in the opening phrase and the bridges between the sections?

Pianist Anne-Marie McDermott was soloist in the Bach Concerto No. 5 in F minor. Here, a little more authentic baroque rigor would have helped.