Footage from Top of the Pops feared lost for years is expected to fetch thousands at auction.
The 1970s clips feature performances from the likes of Elton John, Status Quo, Elvis Presley and Roxy Music.
At the time it was common for the BBC to record over old shows to save money on film.
But a mystery music fan - known only to be from somewhere in Wales - saved them with a Sony CV-2000, one of the earliest home video recorders.
"All we know about the chap is that he was from Wales and that the tapes were acquired by a company that specialises in finding, saving and restoring lost television footage," said auction manager Dan Hampson.
"Back in the '70s his family probably wondered why he was spending every Thursday night in front of the TV with a huge piece of equipment, but now people are glad it has been saved."
Mr Hampson, of Omega Auctions, in Merseyside, said the lot had attracted plenty of interest.
"There are 150 performances over 34 tape reels," he said.
"There are snippets of full songs and also links as well."
The recordings are expected to sell for between £5,000 and £8,000.
The auction is to be held on 8 September.