I've just noticed this thread and regretfully don't have time at the moment to take onboard all the very obviously interesting previous postings, so I'll just relate my own approach to sourcing songs.

I'm a revivalist singer of traditional songs and carry about 50, mostly learnt from other revival singers of the late 60s/early 70s such as A L Lloyd, Peter Bellamy, Shirley Collins and Ann Briggs etc. They were my introduction to folk music (via Prog Rock and Folk Rock) and have remained my reference point, along with the source singers to which they were close.

The tunes were almost all learnt from recordings as I'm only just learning to play an instrument from written music. The words came either from these sources or from a few staple publications such as the 'Penguin Book of English Folk Songs'. I think only two of my songs came entirely from books and I had to use Noteworthy Composer to capture the tunes.

Richard