It's unfathomable that a mere three notes in a simple rising sequence should unfold into a masterpiece. But as anyone who has heard Samuel Barber's String Quartet in B Minor performed by the St. Louis Symphony in the delicious soundtrack to the film "Platoon" or happened to hear the Shanghai String Quartet play the original version Tuesday night at the Kennedy Center Terrace Theater will tell you, three notes and a lot of soul is all it takes.

The Shanghai's performance served best to illuminate the tragic nature of the adagio's tender simplicity. Its reticent glow appealed all the more because we heard one instrument to a line -- and not the massed strings of a symphony orchestra. Somehow, a split-second lack of synchronization made the performance that much more human, and therefore humbling.

Artists who put music before ego will always supply the best performances -- which is why pianist Lilian Kallir, who joined the Shanghai Quartet in Schumann's Quintet for Piano and Strings, Op. 44, was so effective.

Kallir never overshadowed her colleagues, but weaved her lines with wistful grace, grave beauty or doleful resonance -- whatever the music required at the time. Her sensitivity was matched perfectly by the entire quartet, though violist Zheng Wang, whose voice spoke from the belly of the instrument, was simply stunning.

Beethoven's String Quartet in G, Op. 18, No. 2, could have been written for this ensemble, which filled the whole with a generous, convivial exuberance. Vivid but never headstrong, polished but never glib, the Shanghai Quartet let this music speak for itself. Beethoven was the message, and these four artists the happy and talented medium.