It's the modern festival experience: Ben Watt from Everything But the Girl giving a talk on a book he's written about his parents, following Paul Morley speaking on David Bowie, above a pub in Aldgate East. Increasingly, rock music is a literary pursuit – these kind of salons are popping up all over the place as the industry tries to get its legacy in perspective, but the Irish festival Other Voices has been holding "banter" sessions for years (past subjects have varied from discussions on masculinity to lessons in how to grow your own vegetables). Last weekend, Other Voices made its London debut at Wilton's Music Hall, in partnership with the Barbican. In essence the festival is an intimate live TV broadcast for the Irish channel RTE, with seats offered to the public through a lucky draw. There are tight, 45-minute sets from a dozen acts from Laura Mvula to Laura Marling, John Grant to Matthew E White. There's an unspoken no-old-stuff policy, and an invitation to use the slot as a testing ground for new material. Imelda May reads lyrics scribbled on foolscap paper in the back of her cab from Kentish Town, and Derry-born, 16-year-old SOAK has a song so new it's just called New Song.
The venue, nestling in the shadow of a tower block next to a Victorian school for seamen's children, is the oldest surviving music hall in Europe, and the Barbican has been putting on shows here for a few years now. The stage is cast in a soupy vert-de-gris glow, and amid the peeling paintwork there are frescoes of ladies playing exotic flutes and sitars, recalling the days of the East India Company and the 19th-century gentlemen – the Pips and Dorian Grays – who came here to indulge their darker sides.
In short, Wilton's Music Hall has seen stranger things than Kevin Rowland, and the colourful grotesquerie of Dexys and their latest album, One Day I'm Going to Soar, suits this space on Saturday evening: there he is, in a clinch with his leading girl (the actress Madeleine Hyland), part dirty uncle, part Dirk Bogarde in Death in Venice. The band's vintage aesthetic has settled on baggy pants and Hawaiian shirts of late: there are costume changes – someone will disappear and make a grand entrance in a different flat cap – which, together with all the melodrama, makes for a pleasingly am-dram experience ("Kevin, don't talk to me, I don't even want to see you!"). You're so close to the musicians in this venue, you can see how hard they're working, her mascara streaked with tears, him trembling on one knee. Geno is pulled from its classic, swaggering pace and worked up into a kind of Cuban rumba. Generally, Other Voices doesn't have much time for old songs.
"Everyone's a musician now," says someone in the pub, "just as everyone's a photographer and a writer – but ultimately the cream continues to rise to the top." SOAK (she once said her name came from "a mixture of soul and folk") is the latest in a long line of acts to sign a major record deal since her first appearance at the festival. Villagers' loyalty to the "brand" is obvious when Conor O'Brien turns up for a solo set, adapting the lavish arrangements of their latest album, Awayland, for his tiny acoustic guitar in a state of trance-like, almost meditative concentration. His songs bob along on a stream of abstract thought, untethered by clear verse-chorus structures, and he chews over his words like an Irish Alex Turner – another young writer made older somehow by the power of wit.
It's heartening to see how quickly someone can go from newcomer to "conquering hero" on the strength of one album, and Saturday night really belongs to John Grant, whose Queen of Denmark was the "cream" of 2010, a debut so memorable that, unusually, the public really cared what he did next. Grant, who used to work as an interpreter and collects languages the way old ladies collect walking-stick badges, recorded his follow-up, Pale Green Ghosts, in Iceland and got himself a new band there – all of whom look a little bit like him, and make a burly team of men singing in harmony about his past loves. He's one of the great rock'n'roll personalities of recent years: needy, confessional, sardonic, lovable – his voice wraps you up in a warm golden fleece and rolls you in space dust. But this close-up performance reminds you what a careful musician Grant is, and how much of his humour is rooted in that strange precision – in his habit of compressing long thoughts into tight tunes, or seating himself regally at his synth and playing just five or six notes that ring out like the theme from a cosmic scene in a 70s Bond movie. His band attack the vast bank of nobs and effects pedals as if it were an orchestra, and Wilton's turns into a cavernous sound lab where everything digital seems to be living and breathing.
There are flashes of exotic life – a hippie commune in Richmond, Virginia, to be exact – with Matthew E White's headline set on Sunday night. Introduced by the actor Aidan Gillen as "big, groovy, loose, sexy, spacey", White deals in a kind of lush, psychedelic soul-rock that is so brimming with pleasure – so utterly "switched on" – it's only mildly irritating you can't hear a word he's saying because his drummer is too loud. This is their debut television performance and they seem to be on another planet – watching them sashaying, grooving, grinning, you just want to be in that band.
It makes you wonder about Paul Morley's prediction, back in the pub, that the rock music of the future will be something utterly unrecognisable, bizarre, something we simply can't imagine yet. The best acts at Other Voices are proof that to make music sound new, you only need to play as though it's never been done before.
