The Academy of St. Martin-in-the-Fields, with 16 members, is about as small as an ensemble can be without forfeiting the title of "orchestra." It is also remarkably well-known in the United States, where it now is making only its second tour. A large and enthusiastic audience flocked to the Kennedy Center Saturday night to hear and warmly applaud these fine musicians.

The program ranged through three centuries, showing remarkable versatility in an ensemble identified almost exclusively with 18th-century music. From beginning to end, the playing had a high level of technical polish and stylistic awareness, alert to the subtle differences between Bach and Handel as well as the contrasting styles of Tippett and Dvorak. It was an excellent evening, but it was not quite like the Academy of St. Martin-in-the-Fields that has become world-famous on records.

It probably is unfair--but also inescapable--that musicians in live performance must compete with the memory of their own recordings. The problem is most acute for rock performers, who routinely do things in the studio that they find impossible in the concert hall. But it also afflicts classical musicians--not so much because mistakes can be edited out of a studio recording (the mistakes were insignificant Saturday night) but because a record makes the musicians guests in your home; it creates an ambiance and allows fine details to be heard that easily are lost in a hall with 2,700 seats.

The difference particularly was notable in Dvorak's wonderfully melodious Serenade, Op. 22, which concluded the program. The playing was exquisite, but one longed for a richer tone, a more ample bass sound. I suspect it would have been a glorious experience, rather than merely a good one, in the Terrace Theater. Handel's Concerto Grosso, Op. 6, No. 10, was composed more to the scale of this orchestra, as were Tippett's baroque-flavored Little Music for Strings and Bach's Concerto for two violins. Violinist and music director Iona Brown set a good pace, maintained fine balances and brought out contrapuntal lines with clarity. Musicianship was not the problem Saturday night; the problem was popularity. The Academy's audience can fill larger halls than its sound.