I’M playing Glastonbury tomorrow – well, in a way. Call it a small (potentially very muddy) side-benefit of three years of indyref table-thumping. Brother Billy Bragg has invited me to speak at his Left Field zone (the Left Project’s Cat Boyd is on today), along with ex-London Mayor Ken Livingstone, the head of Liberty, Shami Chakrabarti, and the journalist John Harris. My pal Robin McAlpine, founder of Common Weal, sat on this stage last year. I expect a Daily Mail drone to be hovering over my bins soon, x-raying the contents furiously.

Is this the last residue of Glastonbury’s hippie radicalism? I’m sure we’ll all give it, er, welly (though how much fomenting can be done from a prone position on a literary-festival-style couch is debatable). The headline act later that night is Paul Weller, a man from whom those of a certain generation might expect much, in terms of rousing a rock crowd to righteous anger.

But I’m not overly hopeful. Glasto seems to go in for unspecific, merch-moving epiphany these days. The key controversies are over whether hip-hop or R’n’B are “appropriate” for the big stages (nice dog-whistle politics implied there).

Yet who’d be a rocker (or soulster) with a conscience, and thus a burning message, to deliver to the bouncing tens of thousands – and watching millions – these days? The critical jeering; the outraged TV producers; the managers and A&R men having heart-attacks about their playlist prospects… By the time you get anywhere near the main-stage, you’ve no doubt built up such a web of music-biz dependencies that playing safe (or at least, playing ambiguous) is the obvious option.

Unless, that is, you’ve put a political critique at the heart of your music in the first place: add unassailable sales figures to that, and you might be able to burn through the wet mattress of careerism. I don’t fully check for Muse, but I deeply love the paranoid techno-critique that laces their current “Drones” album. I’d go to see how they answer the Nirvana challenge – “here we are now/entertain us” –with that body of work.

When Hue And Cry played Isle of Wight a few years ago, my partner and I hung around to watch Springsteen and the E-Street Band close the festival. Again, while not enthusiasts, we thrilled to his mastery of the great American music traditions.

But Springsteen hardly needed to slap politics on top of his songs. Call him a multi-millionaire bullshit artist if you wish – and many do – but he has a body of work addressing American inequalities and injustices that goes back 40 years. It’s baked into his art; he’s been unable to stop scratching that itch. So yes, the bathos on The Boss is only a search-query away. But on the day, the way his poetry and passion combined to articulate anger and hope for a better society was an incredibly powerful experience.

PERHAPS it takes a historic thunderclap to compel musicians to get their heads out of their own navels (or for that matter, other people’s). And maybe the times reveal the depth of the artist. Those of us who worship at the altar of the R’n’B colossus D’Angelo have intensified our devotion recently. He has raised his voice to address the Charleston shooting, the Ferguson riots, and the rising social anger gathering around the hashtag #blacklivesmatter.

Again, like Springsteen, D’Angelo has form as a political artist. His recent record, Black Messiah (over ten years in the making) is named after J. Edgar Hoover’s derisory label for powerful leaders of the civil rights movement.

In a recent New York Times article, D’Angelo hooks up with Bobby Seale, one of the founding Black Panthers, to cruise the streets of Oakland, California, the Panthers’ initial turf.

D is full of fire. He cites his song, The Charade: “All we wanted was a chance to talk/’Stead we only got outlined in chalk... Crawling through a systematic maze of demise.” When asked how he feels about the public disorder of the last six months, he replies: “I feel awesome. What people call a riot I call a rebellion. In my humble opinion the word ‘riot’ is used by the media to dismiss or degenerate what’s really happening. Everybody knows the looting and burning is the voice of the unheard.”

Yet his hero, a now elderly Seale, tries to gently temper his young acolyte’s zeal – praising the Federal authorities for launching an investigation into Charleston, urging more action through the ballot box and the raising of black political ambition, even allowing the decency of police in the system (“some are my friends”).

Our drummer in Hue and Cry, Paul Mills, grew up in New Haven in the 60s and 70s, with many of his male relatives in the Panthers.

He describes them as very focused on the attainment of community power. “They were very practical, about economics, developing the place. Not all guns and threats.”

D’Angelo has been joined by the rapper Kendrick Lamar in speaking out against the “systematic” nature of violence perpetrated against the black population. Yet one can barely imagine what kind of new protest music could arise to protest this. A black President regularly hosts the ageing soul heroes of the 60s and 70s in the White House, yet seems to be leaving behind a more racially polarised America as his legacy. When the whole system looks fallen and compromised, a black punk may emerge, just as the early politicised hip-hop of Grandmaster Flash and Public Enemy so inspired D’Angelo.

IS music still powerful and credible enough to be the lens that concentrates the voice of protest? In the indyref, we can’t say that significant Scottish artists didn’t try to write their motivating anthems. Stanley Odd’s Son I Voted Yes, and Paulo Nutini’s Iron Sky (the wee man roaring “Freedom!” at the top of his golden voice towards the end), are the two most notable examples.

But it seemed to me that social media images and memes were the real riffs being played to an audience by motivated artists; and when audiences did gather in halls, they actually wanted to hear the arguments first and foremost. It was also the nature of the cultural Yes movement – young, worldly, constantly checking themselves with their networks – that no-one wanted to be caught writing crude patriotic (or even ideological) songs. Scottish independence is about realising the power we already have, not about resisting the kind of ambient violence currently suffered by black folks in the US For which state of affairs, give thanks and praise.

However, if we can’t find troubadours to speak the sheer denigration of fixed-term benefits, or decry the soul-shrivelling scripts of retail employment, or the evoke the acute disorientation of the refugee in a strange land, then music on this island really will have died, at least from the fists down.

I regularly listen to Loki and the Cartel’s “Knightmare” to be reminded of what’s possible for modern protest music; I’d love to hear your recommendations. Will I find it at the over-mediated, big-name friendly, blissed-out group hug of Glastonbury? Maybe only if Brother Bragg reaches for his Telecaster.

Pat Kane is on at Glastonbury’s Left Field stage, 3-4pm, with Ken Livingstone, Shami Chakrabarti and others