I'm Rory Stewart and I grew up wanting to be a hero and I'm still fascinated by the ideas of heroism.

In my new series, I'm taking in the long sweep of history from Achilles to Zelensky and asking, what is a hero?

Simply doing your job, being a decent human being.

A true hero is someone who just kind of shines by their own light,

and that light is to be recognised by others.

The Long History of Heroism with me, Rory Stewart.

Listen on BBC Sounds.

Thank you for downloading from the BBC.

For details of our complete range of podcasts and our terms of use,

go to BBCworldservice.com slash podcasts.

What do a cereal bowl, our violin and a pumpkin have in common?

Give up? Well, listen to this.

Okay. Give up? Well, listen to this. A Tibetan singing bowl, an Italian violin and a Brazilian berembow.

They may sound very different, but surprisingly they're scientifically similar.

In discovery on the BBC World Service, percussion and stringed instruments, the way they make and amplify sound.

Humans seem to have a habit of using the most unlikely of objects to make music,

hitting, bowing or plucking them to see what sound they make.

One day a bored woodcutter must have noticed how their saw rang like a bell and decided to exploit the ethereal sound.

Sarah Anglis is a musician and an acoustic engineer.

I'm playing a traditional European instrument, which is the saw.

So this is a saw like you would cut logs up with it. It's quite a big saw, though, isn't it? It is a saw that you'd cut logs up with, yeah. You don't tend to see saws this long anymore. This saw is getting on for a metre long. And what you were doing, you had the handle, wedge between your knees, and then you were bending the saw round into an S shape. And then you've just got a normal cello bow, is that? Yeah, I've got a bow.

A grip. and then you were bending the saw around into an S shape and then you've just got a normal cello bow is that?

...