The American composer Leo Sowerby died on July 7, 1968. At first there were three ways of contacting his heirs: 1. via the Sowerby Foundation, run by his friend Francis Crociata. They had a newsletter, a website, etc. But Mr. Crociata has since passed away, the website has disappeared, and anything sent to their old address bounces back. 2. His executor was Ronald Stalford who though not a relative himself, knew hot to contact the heirs. Mr. Stalford has since passed away and I have been unable to find out who took his place as executor. 3. The Washington National Cathedral, where Dr. Sowerby worked for the last several years of his life, used to know how to contact the heirs, but has lost touch with them.
I want to copy a handwritten manuscript on file at the Library of Congress. Without permission from the copyright owner, they'll let me look at it, but that's it, and I need a copy for some research I'm doing.
Are there any provisions for copying if, following reasonable diligence, the copyright owner can't be found?