Here’s a snapshot of four guys who don’t know whether they’re coming or going. Barely have Bloc announced another hiatus before they unleash a quintet of pretty rousing tracks which belie years of stagnation.

Structurally, the EP captures them at their most bipolar: hope wrestling with fatalism; Kele Okereke’s lyrical self-loathing an uneasy bedfellow with some lain back, why-the-hell-not violent guitar rock which recalls Bloc’s salad days.

The whole thing’s so emotionally jagged that it’s impossible not to be drawn in. The opener ‘Ratchet’ is an immediate, close mix, which grinds out several bellicose guitar figures; Kele promising to ‘make it loud, make it proud, make it count’. But seconds later we’re lurching into melancholy with ‘Obscene’, whose wobbly, trip-hop beat and soulful colouring are full of nostalgia.

But then, in ‘French Exit’, it’s back to devil-may-care chord thrashing: ‘is it really so bad if this is the end? […] At least we had fun’. Its philosophy of acceptance continues on the closer ‘Children of the Future’ – a sort of deathbed speech which urges the next generation to ‘be all we never were’.

But that’s not before ‘Montreal’: an elegant instrumental tour de force, wherein the frontman steps aside and the others shout out that actually, there’s life in them yet.

Compellingly dysfunctional.

At the height of their powers, Bloc Party have just as capably crafted sublimely soft, down-tempo moments as they have blistering dancefloor ammo, bouncing up and down the scale like pinballs. The Nextwave Sessions also bungees across this scale, but the quality only intermittently justifies the whiplash.

Single ‘Ratchet’ is a suitably crash bang whollop opener, an entire firing range of guitar, drum and electro beats shooting off in all directions, but despite this it’s strangely plodding, especially compared to ‘Flux’ or ‘Banquet’. With lyrics like “make it loud, make it count”, I was left wishing the band would show, not just tell.

A few tempo changes later, ‘Montreal’ is worth the wait: a calm, meditative track with beautifully delicate bass guitar and a soundscape which conjures a hazy, endless desert or a waking, snow-clad city like, um, Montreal. Kele is being urged to come home but when he sings “it’s not my home anymore”, it sounds like a band in limbo. Undoubtedly the highlight.

‘Children of the Future’ closes, leaving the EP worryingly near the middle of the road (there’s a smattering of folky acoustic guitar which I would never associate with them). Kele sings “children are the future […] they’re the next wave”, which is of course true but makes you wonder if that’s them throwing in the towel.

‘Montreal’ proves there could be life in Bloc Party yet, but The Nextwave Session sounds like they’re still deciding.

The cover of Bloc Party’s Nextwave Sessions EP is a kind of faux-New York abstract expressionist splatter painting – a thick brush of pastel blue and with a scattergun rippling of colours on top, the kind of thing of thing you’d expect to see a MOMA. It’s actually quite analogous of the record itself, which presents itself as a conflict of ideas and sounds, some pleasing, some, well, just a bit messy.

The lead single Ratchet falls into the latter category, a grimy, bass-laden clusterfuck of lyrical nonsense. The kind of vernacular he uses in the song – “Whatcha’ gonna show me fam?”, “Tell your bitch to get off my shit” – sounds achingly contrived, as if Kele and the lads got together and thought “What can we make for the clubs?” It thumps along well enough, but they don’t have any ownership of it, it just sounds tired and forced.

What they do have ownership of, however, is the melodic, sparse, electro-pop of Obscene and Montreal, which hark back to the best moments from Silent Alarm. Obscene in particular really showcases Kele’s voice for the unique instrument it is, while the swelling guitars and tip-toeing drum-beat on Montreal call to mind a kind of late-90s American-indie vibe, not a million miles from Transatlanticism-era Death Cab For Cutie.

It’s hard to learn a lot from an EP – much of the time they can be filler to placate fans between records, other times they can tread the waters as a group moves from one sound into another, and indeed the title of this would suggest the latter. However, listening to it, it’s still not clear what the next wave of Bloc Party is going to sound like.