 Thousands of people are asking me how I spend my time in London City. Dedicated to the preservation of all forms of our cultural heritage, the British Library is home to the National Sound Archive, an extraordinary collection of over six million recordings of speech, music, wildlife and the environment from the 1880s to the present day. As a research centre, the British Library allows people to ask new questions of old materials. A recording might be made for entertainment purposes, but it might serve a completely different purpose in a research archive. So we like to make things as widely available and as openly available as possible. This is the sound of a bombing raid on the 20th of April 1943. Well, I remember that, actually. To have experienced that night after night. I mean, it's really unimaginable for my generation. They brought it back to me, I must say. Really? Yeah. And what about natural history sounds? If you really wanted to play an evocative sound, what would you choose? It's a lovely example of mimicry. This is a form-breasted bower bird. This guy was having a tin roof repaired, and this bower bird came up and started to imitate the sounds of the workmen. That's terrific. I like the human voices. They can't actually make out what they're saying, but no doubt they're human voices that he's imitating. Exactly. One of the biggest challenges we face is the need to preserve everything we have digitally within the next 15 years or so. After that time, we suspect that the equipment required to play these old formats will largely no longer be available, or it will be too expensive to operate. The content will be lost forever. Would it be true to say that with every day that passes, there is a recording here that's becoming gone? We do pull recordings off the shelf with the intention of playing them, to preserve them, and find that we're too late. We're frantically buying up all the old machines. We're trying to maintain the skills required to operate them and to service them and to ensure that everything's working properly. And that must be tragic, really, because there lies a mute body, as it were, that once spoke and can no longer speak, because you weren't there in time to collect it. It's heartbreaking because every recording is like a universe, essentially. It contains its own logic. It contains its own record of the people, and to see it but without being able to hear it is really heartbreaking. This is the call of a species of Hawaiian honey eater. It's a recording of the last male summoning his mate from an old nest site. The species was eventually declared extinct in the year 2000. It's too late to save that Hawaiian honey eater itself, but there is still time to save the poignant recording of its song. And indeed, the millions of other unique recordings held in audio collections like this one throughout the United Kingdom. But we need to act fast and we need your help. Please support us and help us save these extraordinary recordings so that future generations can connect with the sounds of the past.