In the UK, the Data Protection Act covers the transmission to a third party (eg YouTube, or the Bluegrass Police, etc.) of images or recordings, and if you don't have permission of the subject, it's not kosher.

In terms of protocol, there's a difference between making an audio recording (on a 24-bit digital perhaps) that you intend to share with the performers in a folk club, and which I think most would be enthusiastic about, and making a video recording to add content to your own YouTube channel or whatever.

But if the OP is just wondering about recovering or deleting the stuff already recorded, I think the US equivalent of the Data Protection Act, if such exists, might be the way to go. And anyway, Google at least are very tight about disputed copyright if you were to complain about his online postings.