At the dawn of the 20th century, now firmly installed as the most powerful musician in Europe, Gustav Mahler bade farewell to his youthful "Wunderhorn" period, to embark on a tempestuous final decade of love and death, ecstasy and despair. To end this week's exploration of Mahler's early years, Donald Macleod introduces a complete performance of the composer's serene Fourth Symphony, the pinnacle of his first compositional period and his most profound fusion of song and symphony before "Das Lied von Der Erde", a decade later.