In the last few weeks of his sadly abbreviated life, Franz Schubert noted down some sketches for a 10th Symphony -- not merely "Unfinished," like his very substantial No. 8, but almost "unbegun." Though fragmentary, those sketches "are fairly complex and of great beauty," according to fellow composer Luciano Berio, who knows complexity and beauty when he sees them. He believes they "add a further indication of the new paths that were taking Schubert away from Beethoven's influence." And he became so fascinated ("seduced," he says) by the sketches that he finally worked them into a new piece called "Rendering," containing three movements of symphonic length.

This work, brought to the Kennedy Center Wednesday night by the Royal Concertgebouw Orchestra of Amsterdam and music director Riccardo Chailly, proved to be as fascinating as any music heard in that hall this year. As one expects in any work of Schubert (or, relatively speaking, of Berio), it was rich in melodies -- stirring, noble, winsome, warm, even grandiose. It showed relatively little sequential logic -- not even the rather quirky kinds of logic for which both composers are known -- but that is to be expected in a collection of fragments. To link the fragments, Berio composed bits of what he called "connective tissue," including allusions to some of the other works of Schubert's last year.

A lot of this fascinating music's interest and an approximation of structure derive from the contrasts between Schubert and Berio that make this music sound both old and new. Last night it sounded newer than it was supposed to. Berio's orchestration, in this performance, seemed to include a sound that he was certainly capable of requiring but in fact didn't -- a curious, disembodied high note that rode, sostenuto on top of everything else that was happening on the stage. It was not Berio's work, however, but feedback from someone's hearing aid. The sound was turned off in the Brahms Fourth Symphony, which closed the program, and those who enjoy electronic sounds had to settle for an occasional wristwatch or pager beeping.

In the Brahms, and in Rossini's "Semiramide" Overture, which opened the program, the Concertgebouw gave exemplary performances (give or take an odd horn bobble or string portamento). Chailly gets from this orchestra a tightness of ensemble seldom heard in the Kennedy Center and a wealth of vivid, well-controlled power. It richly earned the long ovation that closed the evening with two encores.