Vic, I would always acknowledge that both Jeannie and Lizzie made conscious choices about decoration, but it remains my conviction that those choices could be made on a particular day and could vary according to life circumstances. IMO they had worked their way to control of the whole range of effects, so that THE choice on THE day would be entirely down to their instinctive response to what was happening.

And JHW, I do believe that this happens (reading from words), though I'm thankful to have little experience of it! But I'd like 'latecomers' to have the opportunities that we had in the 50s/60s to gain the confidence to join in -- though I would be irritated if reliance on crib sheets removed any responsibility for getting to grips with the songs…
(I've just been re-watching TMSA's video of songs from Norman Buchan's '101 Scottish Songs' which was re-launched in January this year at Celtic Connections in Glasgow, and all the artistes on stage as well as the audience are joining in choruses without prompting -- as well as some of the verses too!). To me, this proves that familiarity creates a new, shared experience.

Finally, to return to Vic's comment about Jeannie slowing her singing -- I have a paper from Ailie Munro ( School of Scottish Studies in Edinburgh University) which addresses the problems of Jeannie's pacing. She compares early with later recordings and notes a significant slowing of pace, but it's not entirely clear that academic praise is the root cause, because there were also health concerns, which were outwith Ailie's remit.

(But, faster or slower, I'm delighted to have had the experience of hearing Jeannie Robertson live!)