Like a venomous snake with its head chopped off, Sepultura has been writhing along for more than a decade minus singer-guitarist Max Cavalera, who acrimoniously quit the pioneering Brazilian metal group in 1997 to form the successful Soulfly. Since then, Sepultura has been in a slow, steady downward spiral. Kairos, the band’s sixth album featuring Cavalera’s barely adequate replacement, Derrick Green, isn’t going to alter that trajectory. But Kairos still has aspirations. Where Sepultura’s last full-length, 2009’s A-Lex, is an ambitiously flawed album based on Anthony Burgess’ A Clockwork Orange, Kairos is just a bunch of songs. And yet the group claims there’s a concept of sorts. Allegedly containing a self-absorbed storyline that ponders the subjectivity of time as filtered through the band’s tumultuous, 27-year history, Kairos is sprinkled with bland ambient interludes and spoken-word blather. The meat of the disc, though, is tough and flavorless, strung together by Andreas Kisser’s exhausted guitar repertoire of thrash riffs. That said, Kairos features a fair amount of strength and suppleness. But at this point in Sepultura’s career, it feels likes muscle memory.