Julia Fischer, young, beautiful, and from Munich, is playing the Beethoven Violin Concerto with the Philadelphia Orchestra. During Saturday's performance I could not keep Yehudi Menuhin from mind. The program didn't mention him, so the next morning I looked up her website and discovered that in her teens she won two international Menuhin Competitions under the violinist's supervision. The Beethoven concerto was Menuhin's signature piece, and Ms. Fischer's interpretation, while every bit her own, conveys a radiance & purity that recalls the late artist.