A rare recording of a "carol plygain" - the traditional Welsh Christmas carol - has been found in the British Library in London.
Benjamin Davies was 80 years old when he was recorded
The discovery was made by Wyn Thomas of the University of Wales, Bangor, when he was invited to view a mystery collection in the library's cellars.
He said he was delighted to find recordings from 1910-1913, by folk song collector Lady Ruth Herbert Lewis.
It is the first time the music has been heard in at least 50 years, he said.
Mr Thomas was at the library working on another project when he was invited by staff to view an unknown collection housed in the cellar.
He was told it might be "Scottish or Irish, or even Welsh."
He then recognised the handwriting on the cases as that of Lady Herbert Lewis, the wife of a Denbighshire MP, who lived in Flintshire.
Plygain carols were traditionally sung early on Christmas morning, unaccompanied and only by men.
The stronghold of the tradition was in central north Wales and the old counties of Montgomeryshire and Meirionnydd, but the plygain carol found in London was recorded in Drefach, Carmarthenshire, showing the tradition went much further south.
"Before this discovery there were only six to seven cylinders in Wales, kept at (the Museum of Welsh Life at) St Fagans, so to see this collection in front of me was like a dream," said Mr Thomas.
The sound of Benjamin Davies singing was recorded on an Edison Gem (Model D) by Lady Herbert Lewis in 1913.
It is thought Lady Herbert Lewis' recordings were sent to a friend
As a member of the Cymdeithas Alawon Gwerin (Welsh Folk Song Society) - which celebrates its centenary this year - she recorded as many traditional songs as she could.
She even took the machine with her to India when she visited her missionary daughter, and the collection includes previously unheard traditional Indian songs from that trip.
Phonograph cylinders are made from wax, and although the song can be clearly heard, the passage of time has affected the quality of the recording.
It is hoped that the School of Music at the university will be able to restore the whole collection using modern technology.
"There is no mention of a tree, turkey or tinsel in this Christmas song but rather it's a joyful biblical carol - truly the voices of the past coming back," said Mr Thomas.