Before Beatlemania, there was the distinctive Höfner violin bass — the first guitar that Paul McCartney bought after becoming the bassist for the Beatles.
That bass can be heard on some of the band’s most famous hits, including “Love Me Do,” “She Loves You,” and “Twist and Shout.”
Mr. McCartney picked up the instrument in a Hamburg music store in 1961, and it accompanied the Fab Four as they rocketed to stunning success, becoming the most famous band in the world. But the guitar vanished eight years later.
A new campaign is seeking to find the missing instrument, and hundreds of people have responded, hoping to help solve the decades-old mystery: Where is Paul McCartney’s missing bass guitar?
“It’s a hugely significant instrument in its own right,” said Nick Wass, a semiretired consultant for Höfner, the guitar’s manufacturer, who has joined forces with two journalists to try and track the guitar down. “It’s the bass that made the Beatles.”
“The bass was absolutely at the heart of the origins of the Beatles sound,” said one of the journalists, Scott Jones, who worked for the BBC. “The smallest pieces of information can often lead to the biggest breakthroughs,” he said of their appeal for tips on its fate.
Mr. Jones’s wife, Naomi, is the other journalist behind what they are calling The Lost Bass Project.
The three Beatles fans have urged members of the public to come forward with any information that might help. No tip is too small, they say, and they are promising to keep sources confidential. They say they have already received several credible leads since the project began on Saturday.
The instrument’s treasured place in Beatles mythology is intertwined with the band’s story. After the departure of their original bassist, Stuart Sutcliffe, Mr. McCartney, who had been playing guitar, switched instruments to replace him during a residency in Hamburg in 1961. For that, he needed a new bass guitar.
“I got my Violin Bass at the Steinway shop in the town center. I remember going along and there was this bass which was quite cheap,” he said in a 1993 interview with Guitar Magazine, adding that he had not wanted to go into debt and could only afford the Höfner, 500/1 guitar at the time. It cost about £30 pounds, or $38, he recalled. “And once I bought it, I fell in love with it.”
Mr. McCartney took the guitar back to Britain, where it accompanied the Beatles through hundreds of gigs — from the band’s early concerts at the Cavern Club in Liverpool, where they were spotted by Brian Epstein, who would become their manager, to the recording of their first two albums. It was repaired in 1964, according to the team behind the new search, and then used along with other bass guitars.
But the last confirmed sighting of the instrument was in London in 1969, in video footage of the band members writing their final album, “Let It Be.” Rumors have percolated ever since about what happened to the instrument: The Lost Bass Project suggests that it could have been stolen or lost either from the basement of Abbey Road Studios, or from the Apple Corps recording studio on Savile Row.
A representative for Paul McCartney declined a request for an interview. But Mr. Wass said he understood, from previous communications with Mr. McCartney, that he was keen to be reunited with the instrument. “He calls it the ancient one,” Mr. Wass said.
Among the leads they had received, Mr. Jones said, were suggestions that the instrument could have traveled to the United States or Japan. But he added that all the leads need to be vetted. “Somewhere among that information there is going to be the answer,” he said.
Other iconic instruments have been lost and found over the years — one close example being a Gibson acoustic guitar belonging to John Lennon, which was bought in 1962 and then lost the following year. Half a century later, it re-emerged and was sold at auction in 2015 to an anonymous buyer for $2.4 million.
It is unclear what the market value of Mr. McCartney’s missing guitar would be, but the team behind the search insists that the effort is not for monetary gain, calling the guitar “priceless.”
“We just want to know where it is,” said Mr. Wass.