The OP said he was worried about copyright. He's right to be, because copyright law is not on his side.

That doesn't mean that these recordings shouldn't be made available. I'm sure they would be of interest to many, and I entirely agree with Jim's attitude of "share away". It does mean that he faces a lot of potential obstacles. However I emphasise "potential". It is probably unlikely that the majority of those he recorded will care about them being made public, and provided he responds appropriately to those who do want them taking down that will probably be the end of the matter.

It does mean that there could be a lot more work involved than just digitising and posting the recordings, as he may also have to spend some time dealing with copyright requests. These are possibly more likely to come from the songs' composers than the performers.

Essex County Record Office has a large number of recordings of Chelmsford Folk Club and other local clubs made in the 1970s and 80s by Jim Etheridge and Dennis Rookard. I would love to hear them, not least because many of them feature me and my friends, as well as some impressive guests. However, even setting aside the costs of digitising them, I suspect copyright would prevent the ECRO from ever putting them online.