So hands up – or perhaps that should be devil-horn fingers up – if you ever expected to see heavy metal performed at the Edinburgh International Festival.

And it's not just a one-off, or just one band, either. There are going to be two. The marvellously named Miserable Faith and Suffocated, both Chinese, are to be part of the Beijing People's Art Theatre version of The Tragedy Of Coriolanus by Shakespeare. Jonathan Mills's penultimate programme really is full of eyebrow-raising bookings such as this. I cannot imagine Mills himself headbanging down in the mosh pit as Suffocated unleash their drop-D tuned riffage. And the festival audience at the Playhouse may have never seen the like before.

But one could imagine, perhaps, if you know your heavy metal, that the more aesthetically sophisticated end of the much ridiculed genre (and yes, there is one, and I personally love it), could have made an entrance at another part of the August festival. Maybe the Fringe could have seen a multimedia event featuring Tool or Neurosis, two terrific American bands who not only extend but embroider the genre's riffage and doom-laden world view with their own genuinely affecting artistic visions. Perhaps the late lamented Isis, another American "post-Metal" band, could have appeared as their masterpiece, Oceanic, feels like a soundtrack to a broader work of art, perhaps one that could be staged or shot in some way.

But at the EIF? Some regular attendees to the EIF may well wonder what is going on. Mills feels that the public will recognise that this year's festival is not as "weird and alienating" as it first may look to some. But with Patti Smith and Frank Zappa, those head-banging metal heads from China and the semi-improvised music of the Bang On A Can All-Stars, this festival has the highest concentration of non-classical music I can remember. It makes for a fascinating mix. It will also be a job for the team at the EIF to sell some of those tickets.

But perhaps seeing electric guitars on stage with opera singers should not be that unusual. It is part of something happening in the broader musical waters. Rock and its more post-rock cousins are climbing further into the world of high art and the avant-garde. It is almost like the 1970s all over again, when guitar bands began thinking in terms of art and the longer time spans of the history of music itself, rather than just rocking out.

Down south, for the first time ever, Glasgow band Mogwai will be performing their spectral soundtrack to Douglas Gordon's Zidane film live, at the Manchester International Festival (as soon as I heard of that particular gig, I wondered whether Edinburgh has missed a trick: I think it has). And only last weekend, the Scottish audience at the Glasgow Royal Concert Hall was treated to the premiere of another piece of rock-meets-art, Radio Rewrite, the new piece from Steve Reich. Reich, as you may have read, has taken two songs by Radiohead – Everything In Its Right Place and Jigsaw Falling Into Place – and, inspired, has created a wonderful new work of modern "classical" music from them. The central slow section, predominantly influenced by Everything's wondrous ennui, was a gorgeous passage of music.

Rock music is fractured and atomised. It may have once felt like there was a central narrative to beat-driven guitar music – from blues to rock'n'roll, from Elvis to The Beatles, from The Beatles to David Bowie – but punk and indie and hardcore shattered all that, and electronic music (which I still perhaps quaintly call "dance music") has overtaken it in popularity. There won't be another punk moment to ridicule and banish the art-rockers of our day, mainly because three-chord punk itself sounds more dated and pedestrian now than, say, Autechre or Mastodon. Reich himself said last week that he thinks the artificial divide between scored and un-scored music is now being closed and healed. Maybe Mills agrees with him.