According to this apparently authoritative website, in the case of sound recordings the period of protection of performers' rights is extended from 50 to 70 years:

Copyrightuser.org

To Matt Milton, it is one thing to sing to a small audience in a folk club, many of whom may be your friends. It is quite another thing for that performance to be broadcast to the whole world. Likewise, someone who is now a polished and experienced performer may not be keen to see their early efforts exposed. So I don't think it can be assumed that those performers won't mind if these recordings are made public, although I suspect most won't be bothered, and many will be pleased and flattered.

The other matter to bear in mind is that composers' rights are largely administered by rights organisations eg PRS who have a duty to their members to generate income where their works are being used - even on a non-commercial basis. They are unlikely to ignore this, assuming it comes to their attention. It is up to the owners of the rights to tell PRS that they are willing to waive them in particular circumstances.

These are issues which are faced by museums, galleries, universities and other institutions who want to make their material widely available. In most cases they take a risk-managed approach. I suggest the OP does the same - put it online, but be prepared to deal promptly and politely with any objections.

It might be possible for the OP to claim a "fair usage" exemption on the basis the material is being made available for private study and has no commercial value. However fair usage is difficult to define and will depend on the facts. The criteria, as established by one court case, include:

(1) The degree to which the alleged infringing use competes with exploitation of the copyright work by the owner. This is likely to be a most important factor…
(2) Whether the work has been published or not…
(3) The extent of the use and the importance of what has been taken. In many cases this will be a highly important factor…’

Whether this would be enough to deter PRS is another matter. I have found them quite difficult to deal with - not unreasonable, but inflexible.