No one in Symphony Center's large audience who heard Vondracek perform this piece last spring with the Lake Forest Symphony would have been surprised at the steely power of his lyrical line. Evenly shaded and always expressive, it was always prominent, even when the orchestra was in full cry and the melody itself was buried in a blizzard of racing chords and scales. For the rest of us, Vondracek's performance was one of those most happy concert experiences, an encounter with a young talent on the verge of a stellar career. His gorgeously tossed-off encore, a flamboyant arrangement of the Pas de Deux from Tchaikovsky's "The Nutcracker,'' was fancy icing on an already succulent cake.