It's day five of the EFG London Jazz Festival, and Snarky Puppy's show at the Roundhouse has sold out weeks in advance. And, as the crowd sings the gorgeous main theme of “Thing of Gold” in perfect unison, one of the reasons for the band's huge success becomes apparent. Yes, there's brilliant musicianship, spirited improv, blazing energy and the kind of impressively vast textures that only a band this size can achieve. But there's something else, which trumps all of these things. There's melody.

You know that thing? That thing that bands of a certain age do? You know… the thing where they get all misty-eyed about past glories and decide to get the band together for one last spin of the big hits? Well, the continuing story of Loop is about as far removed from that as it’s possible to be.

A slim 69-year-old man in a rumpled sports jacket looking like a gone-to-seed history lecturer with the colour-clash dress sense of Michael Portillo is gripping a microphone so hard it’s a wonder it hasn’t been crushed. He is barking lyrics in Icelandic so gruffly that this could be any Celtic or Nordic language.

This is Megas – born Magnús Þór Jónsson – the Icelandic poet, singer and cultural icon who has been ploughing this particular and peculiar furrow since the early Seventies and, in 1977, helped kick-start Icelandic punk. In Iceland, he is an enduring presence.

Brighton’s guitar pop outfit, the Kooks have been churning out largely pleasant but fairly bland songs since their 2006 debut Inside In/Inside Out. Recent album Listen, however, has suggested that things might be changing. Less evident, but not entirely banished, are the unremarkable strum-alongs, with a rawer and funkier groove edging its way into a few of their tunes with some success. Similarly gone is the poodle hair and clothes that made them look like the Verve’s younger, more clean-cut cousins.

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Is it just me, or do Guy Barker's orchestral charts for Jazz Voice get more refined, more nuanced, more richly detailed every year? Effectively becoming earworm central last night, the Barbican resounded with tintinnabulating glockenspiels, delicately plucked harp strings, punchy horn charts and luxuriant strings, as Barker sprinkled his arranging magic over the customary epoch-spanning celebration of anniversaries, birthdays and milestones stretching back from 2014.

Even before Kate Tempest appears, it’s clear this isn’t going to be an evening of slam poetry jamming. Her band walk on, three guys who attack a line-up of electronic kit with vigour, one wielding drumsticks, alongside Anth Clarke, a striking black female MC, who looks like a 2007 nu-raver in baseball cap, white sunglasses and a crop top. They whip up a hammering electro racket before cutting out abruptly when Tempest walks on, all smiles, flowing blonde locks and a low-key black T-shirt. She breaks into “Marshall Law” from her Mercury Music Prize-nominated album Everybody Down.

If a band gets up and says “We are only going to be playing songs from our new album, not actually released here yet” normally most audiences would groan mightily. But somehow Susheela Raman has educated her audience to expect the unexpected. Her somewhat wayward musical path has included Indo-jazz, rock covers, Tamil voodoo music and introspective songs. It has not been one that a manager or record company would have recommended. They tend to like more of the same.

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The voice is unmistakably Icelandic. Fluting and dancing around the notes, the words it carries are broken into segments which don’t respect syllables. Although singing in English, Hildur Kristín Stefánsdóttir hasn’t sacrificed her Icelandic intonation.