Post-punk:

The term "post-punk" was first used by journalists in the late 1970s to describe groups moving beyond punk's sonic template into disparate areas. Many of these artists, initially inspired by punk's DIY ethic and energy, ultimately became disillusioned with the style and movement, feeling that it had fallen into commercial formula, rock convention and self-parody. They repudiated its populist claims to accessibility and raw simplicity, instead seeing an opportunity to break with musical tradition, subvert commonplaces and challenge audiences. Artists moved beyonds punk's focus on the concerns of a largely white, male, working class population and abandoned its continued reliance on established rock and roll tropes, such as three-chord progressions and Chuck Berry-based guitar riffs. These artists instead defined punk as "an imperative to constant change", believing that "radical content demands radical form".

Please answer a question about this article. If the question is unanswerable, say "unanswerable". How many chords are never used in punk music?
unanswerable