He helped define the look as well as the sound of the enduring British post-punk band, which influenced Nirvana, Metallica and others.Geordie Walker, the founding guitarist of the British post-punk band Killing Joke, whose haunting, muscular riffs proved an inspiration to platinum-selling bands including Nirvana and Metallica, died on Sunday in Prague. He was 64.The cause was a stroke, according to a statement the band posted on social media.With his icy good looks, rockabilly-esque pompadour and vintage gold-top Gibson guitar, Mr. Walker helped define the look as well as the sound of Killing Joke during its peak in the 1980s and ’90s.“No man was cooler than Geordie, one of the very best and most influential guitarists ever,” Youth, the band’s original bassist, wrote in a recent Instagram post. “He was like Lee Van Cleef meets Terry-Thomas via Noël Coward.”Mr. Walker’s driving, multilayered fretwork helped propel the dark though often danceable sound of a band that helped pioneer industrial music by blending heavy metal intensity, new wave hooks and a punk taste for provocation. The cover of the band’s 1992 compilation album, “Laugh? I Nearly Bought One!,” for example featured a clergyman exchanging salutes with Nazi brownshirts.Despite its uncompromising approach, the band released five singles that reached the Top 40 in Britain — “Love Like Blood” was their highest charting, reaching No. 16 in 1985 — as well as six Top 40 albums.Killing Joke never found comparable commercial success in the United States, although its 1984 single “Eighties” got plenty of play on alternative rock stations in that era. But the band — and Mr. Walker’s searing guitar work — earned the respect of many artists, including, according to Rolling Stone, Trent Reznor, My Bloody Valentine, Faith No More and LCD Soundsystem.Metallica put its own spin on Mr. Walker’s ferocious guitar work on its 1987 cover of Killing Joke’s 1980 song “The Wait.” More famously, or infamously, Nirvana — big fans of Killing Joke — relied on an ominous riff so eerily similar to Mr. Walker’s on “Eighties” for its landmark song “Come as You Are” that Killing Joke considered legal action.While the tension between the bands eventually subsided — Dave Grohl, the Foo Fighters frontman who had been Nirvana’s drummer, played drums on the band’s 2003 album, called simply “Killing Joke” — Mr. Walker was noticeably tart on the subject when interviewed by Guitarist magazine in 1994. “Kurt Cobain is a bloody good songwriter,” he said, “but a complete plagiarist.”“We are very pissed off about that, but it’s obvious to everyone,” Mr. Walker said. “It’s obvious to everyone. We had two separate musicologists’ reports saying it was; our publisher sent their publisher a letter saying it was, and they went, ‘Boo, never heard of ya!’ But the hysterical thing about Nirvana saying they had never heard of us was that they had already sent us a Christmas card!”Mr. Walker performing with Killing Joke in 2015. Despite shifting lineups and multiple hiatuses, the band, formed in 1979, continued to record for nearly four decades.Lorne Thomson/Redferns, via Getty ImagesKevin Walker was born on Dec. 18, 1958, in County Durham, in the northeast of England, the only child of Ronald Walker, a woodworker, and Mary (Glen) Walker, a bookkeeper. He spent his early years in Chester-le-Street, a town near Newcastle, and acquired his nickname — a term referring to the people and accent of the Newcastle area — while attending Sir Herbert Leon Academy in Bletchley after the family moved to southeast England.Mr. Walker was an avid guitarist as a youth, but he had never played in a band until he moved to London in 1979 after graduation to study architecture. He answered an advertisement in Melody Maker, the influential British magazine, posted by the singer Jaz Coleman, who was looking to start a band with the drummer Paul Ferguson.“It looked rather serious, fanatical,” Mr. Walker said in a 1984 interview. “It clicked with me.” Killing Joke released its first EP, “Almost Red,” in December 1979.Despite shifting lineups and multiple hiatuses, Killing Joke continued to record for nearly four decades. During those breaks from the band in the 1990s, Mr. Walker formed the band Murder Inc. with Chris Connelly, the lead singer of Revolting Cocks, along with other members of Killing Joke but without Mr. Coleman, and the Damage Manual, featuring Mr. Connelly along with Martin Atkins and Jah Wobble from Public Image Ltd.At a party after a Killing Joke concert at Saint Andrew’s Hall in Detroit in 1989, Mr. Walker met Ginny Kiraly, a college student and model. The two married six months later. After the birth of their son, Atticus, in 1992, the family settled in suburban Detroit, where they stayed until the mid-2000s, when Mr. Walker returned to England to care for his ailing father and the couple split. They divorced in 2012.Mr. Walker is survived by his mother; his son; his partner, Alexandra Kocourkova; and their daughter, Isabella.Despite its British chart success, Killing Joke never reached the commercial pinnacle. But as Mr. Walker once put it in an interview with the music writer Andrew Perry, he was not sorry to have missed the perils of rock stardom.“If it had all gone according to plan,” he said, “we’d have all been dead by 1986.” More