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. Today, new science in the field of birdsong is transforming those long-held ideas. Scientists are discovering that, in fact, in the majority of all songbird species, females sing - and it is only now they are being properly heard. Through this revelation and others, we can understand that animal songs are marvelous examples of the spectacular survival strategies that species have developed in order to stay alive.