Background: Joy Division were an English post-punk band formed in 1976 in Salford, Greater Manchester. Originally named Warsaw, the band consisted of singer-songwriter Ian Curtis, guitarist and keyboardist Bernard Sumner, bass player Peter Hook and drummer Stephen Morris. The band was formed by Sumner and Hook after attending a 4 June 1976 Sex Pistols concert at the Lesser Free Trade Hall in Manchester. While Joy Division's early recordings were heavily influenced by early punk, they evolved a unique sound, aided by producer Martin Hannett, which earned their reputation as pioneers of the post-punk movement.
Context: Joy Division's style quickly evolved from their punk roots. Their sound during their early inception as Warsaw was described as generic and "undistinguished punk-inflected hard-rock". Critic Simon Reynolds observed how the band's originality only "really became apparent as the songs got slower", and their music took on a "sparse" quality. According to Reynolds, "Hook's bass carried the melody, Bernard Sumner's guitar left gaps rather than filling up the group's sound with dense riffage and Steve Morris' drums seemed to circle the rim of a crater." According to music critic Jon Savage, "Joy Division were not punk but they were directly inspired by its energy". In 1994 Sumner said the band's characteristic sound "came out naturally: I'm more rhythm and chords, and Hooky was melody. He used to play high lead bass because I liked my guitar to sound distorted, and the amplifier I had would only work when it was at full volume. When Hooky played low, he couldn't hear himself. Steve has his own style which is different to other drummers. To me, a drummer in the band is the clock, but Steve wouldn't be the clock, because he's passive: he would follow the rhythm of the band, which gave us our own edge."  By Closer, Curtis had adapted a low baritone voice, drawing comparisons to Jim Morrison of the Doors (one of Curtis's favourite bands).  Sumner largely acted as the band's director, a role he continued in New Order. While Sumner was the group's primary guitarist, Curtis played the instrument on a few recorded songs and during a few shows. Curtis hated playing guitar, but the band insisted he do so. Sumner said, "He played in quite a bizarre way and that to us was interesting, because no one else would play like Ian". During the recording sessions for Closer, Sumner began using self-built synthesisers and Hook used a six-string bass for more melody.  Hannett "dedicated himself to capturing and intensifying Joy Division's eerie spatiality". Hannett believed punk rock was sonically conservative because of its refusal to use studio technology to create sonic space. The producer instead aimed to create a more expansive sound on the group's records. Hannett said, "[Joy Division] were a gift to a producer, because they didn't have a clue. They didn't argue". Hannett demanded clean and clear "sound separation" not only for individual instruments, but even for individual pieces of Morris's drumkit. Morris recalled, "Typically on tracks he considered to be potential singles, he'd get me to play each drum on its own to avoid any bleed-through of sound". Music journalist Richard Cook noted that Hannett's role was "crucial". There are "devices of distance" in his production and "the sound is an illusion of physicality".
Question: What was their style of sound?. Whats the answer?
punk-inflected hard-rock