It is almost inaccurate to characterize a Washington Bach Consort event as a concert in the conventional sense. Music director J. Reilly Lewis does conduct. But Lewis also presides, with his cheery little speeches about Bach, in the manner of a benign pastor before his congregation. And last night's packed house in the Terrace Theater reveled in it.

Lewis' repeated statements about the "unique variety of Bach" (sorry 'bout that, Mozart and Beethoven) could become cliche's, except that almost invariably Lewis keeps the music going until he has proved his point. Last night's concert was 2 1/2 hours long, and it was in two of the encores that the evening reached its most exalted points -- each with full orchestra and chorus (that's about 50 people).

The first encore was a curiosity, and a glorious one. It was a chorus called "Der Gerechte kommt nein" that technically broke the Bach Consort's rules, which are to devote themselves exclusively to the performance of every last note the great man ever wrote. This music was by Johann Kuhnau, who was Bach's predecessor at Leipzig's St. Thomas Church. Bach thought sufficiently well of this grave, measured work that he rearranged it, and that is what was heard.

After that, the consort followed with one of the dozen or so greatest of all Bach's 389 chorales, the conclusion of the St. John Passion -- a creation built on startling modulations that seem to open the way to some kind of otherwise unutterable spiritual truth.

The outstanding performance on the regular program was of the Fourth Brandenburg Concerto, with a steady pulse and particularly fine solo playing by violinist Jody Gatwood and recorder players Scott Reiss and Jesse Lepkoff.

The evening's cantata was an early one, "Gottes Zeit ist die Allerbeste Zeit," BWV 106 ("Actus Tragicus"), with the composer characteristically eloquent on the subject of death -- nicely performed.