Charles Hazlewood is joined by the BBC Scottish Symphony Orchestra to reveal the musical and emotional depths behind two very different birthday serenades. Wagner composed his "Siegfried Idyll" as a surprise greeting for his wife Cosima which she heard wafting to her room from the stairs on her birthday. He based the work on themes from his latest opera. The young Peter Warlock's boyhood hero was the composer Frederick Delius, whose 60th birthday he marked with a short Serenade for strings, composed in pastiche style, but with his own personal twist.