Jack, it was probably "Caneuon Llofft Stabal" - Stable loft songs - a Sain product in co-operation with the National Museum of Wales, which holds the archive tape materials. It was reissued a few years back, I think bundled with the other 'sister' volume of Plygain Carols. Most excellent collection to have. I always point to these traditions as the roots of the Welsh male voice choir (and more interesting to me, personally). Pity no one did similar work in the female tradition ...

siân