In 1972, the composer Leonard Bernstein returned to Harvard, his alma mater, to serve as the Charles Eliot Norton Professor of Poetry, with "Poetry" being defined in the broadest sense. Delivered in the fall of 1973 and collectively titled "The Unanswered Question," Bernstein's lectures covered a lot of terrain, touching on poetry, linguistics, philosophy and physics. But the focus inevitably comes back to music - to how music works, or to the underlying grammar of music. The lectures run over 11 hours. They're considered masterpieces, beautiful examples of how to make complicated material accessible.