Overview: Leonard Bernstein celebrates Mahler's centennial by conducting excerpts from the composer's Fourth Symphony in G and discussing his career as a composer and conductor. Soprano Reri Grist joins the orchestra in a performance of the last movement of the Fourth Symphony. William Lewis sings "Youth" and Helen Raab sings from "The Farewell," both from Mahler's The Song of the Earth (Das Lied von der Erde).