If they aren't released by the current copyright holder within 25 years of recording, the copyright reverts to the artist[[s) - as I understand it. I suppose that means the artist could choose to release it himself. But they're being held back because we don't think the artist would WANT it to come out ... tho' I admit the artist [[or his heirs) isn't consulted in each case. There is quite a sizeable budget for these big annual releases, but it doesn't stretch that far!