A joyful evening of Wagner and Mahler from young maestros

In all of Western music, few C major chords are as ample, radiant and filled with joyful portent as the ones that open the Prelude of "Die Meistersinger von Nürnberg," Richard Wagner's opera about the practice and love of music. Saturday night at the Kennedy Center, those chords signaled the beginning of the final concert of the National Symphony's Summer Music Institute Orchestra, composed of more than 60 gifted young musicians ages 14 to 21, competitively chosen from 27 states and Canada. The...