Sir David Attenborough chooses his favourite recordings from the natural world that have revolutionised our understanding of song. Each one - from the song of the largest lemur to the song of the humpback whale to the song of the lyrebird - was recorded in his lifetime. When Sir David was born, the science of song had already been transformed by Charles Darwin’s theory of sexual selection: singing is dangerous as it reveals the singer’s location to predators, but it also offers the male a huge reward, the chance to attract a female and pass on genes to the next generation. Hence males sing and females don't.