AC/DC ( B24 )

 In the opinion of Stephen Thomas Erlewine of AllMusic, they are "one of the defining acts of '70s hard rock" and reactionary to the period's art rock and arena rock excesses: "AC/DC's rock was minimalist – no matter how huge and bludgeoning their guitar chords were, there was a clear sense of space and restraint." According to Alexis Petridis, their music is "hard-edged, wilfully basic blues-rock" featuring humorous sexual innuendo and lyrics about rock and roll. Music academic Robert McParland described the band's sound as being defined by the heavy rock guitar of the Young brothers, layered power chords, and forceful vocals. "For some, AC/DC are the ultimate heavy metal act", Tim Jonze wrote in The Guardian, "but for others, AC/DC aren't a heavy metal act at all, they're a classic rock band – and calling them heavy metal is an act of treachery." On the controversy of categorizing their music, McParland wrote:

AC/DC will assert that they are not specifically a metal band. Their music—loud, hard, and guitar driven—may best be described as hard rock. However, there are people who will say that they are indisputably metal. Therein lies the ongoing problem of categorization. While AC/DC has referenced the underworld and they have given their listeners 'Highway to Hell' and 'Hell's Bells,' their songs are constructed on straightforward major and minor power chords. They are not modally developed as are a good deal of heavy metal compositions. Their sound is loud and crisp, not muddy or down-tuned.

According to Vulture music journalist David Marchese, the instrumental foundation of the band's simple sound was the drummer—Rudd, Wright, or Slade—striking the kick drum on the first and third beat of every measure, and the snare drum on the second and fourth beat; bassist Williams consistently downpicking an eighth note; Angus Young performing lead parts that possessed "a clear architecture and even sort of swing, in a frenzied, half-demented way"; and Malcolm Young's "propulsive" yet nuanced rhythm guitar featuring "little chuks, stutters, and silences that give the monstrous riffs life".

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