An interesting programme last Friday, I thought, worth looking out for the (inevitable) repeat showing if you missed it. It was a history of the harp from Egyptian (they had someone playing a modern reconstruction -- a very odd tone!) to modern times.
I was fascinated to see the different ways people have tried to make it into a more flexible instrument (I forget the term they used... chromatic?) by adding extra courses of strings, mecahnical mechanisms to change key, etc. I always thought the harp was something really basic and your only choices were how big you want it
I was also surprised to find that it is a hugely popular instrument in South America, where it is a staple of cowboy's dance bands!
And the really cool part was the American composer (I forget his name) who is composing for what I guess you would call "prepared harp" and is combining electronics such as playing the strings with an e-bow!