A story to follow on from the above :
The late Jim Reid, that great singer from Arbroath told us this at Blairgowrie Folk Club in the early 1970s. Jim was in a trio at the time whose name escapes me, but they were driving north on the A9 to do a gig in Aviemore, when they spotted some travellers camped beside the road. They stopped the car, went over and explained that they were interested in traditional Scottish songs, did they, the travellers, know any ? One of them sang a few songs for Jim and the lads, who then asked where he got the songs from.
"Och, I got them off a couple of "Corries" albums" :)