You might find this interesting if you didn't catch it on the BBC last night - the Story of the Guitar, the first of a three part series (now available on BBC iplayer: http://www.bbc.co.uk/iplayer/episode/b00dyhyt/
It seemed to suggest the the popularity of the guitar grew a few centuries ago because ladies of the street sang bawdy songs with guitar accompaniment!
How so little has changed! There's a bit of Paco Pena playing flamenco, an interview with George Gruhn, the Nashville based guitar guru and a really good section on luthier Wayne Henderson showing him making a guitar.
