A single-note drone fills the air, joined by a lilting, pitch-shifted vocal. The mercurial melody falls between folk, plainsong, pop and jazz, the words trigger equally beguiling images and the voice has an uninhibited, freestyle timbre. There are only periodic splashes of additional mutant colour and it’s not until four full minutes that polyrhythmic drums kick in to propel a uncanny, kinetic arrangement that constantly ebbs and flows.

At seven minutes and twenty nine seconds, ‘Hum’ is as audacious as it is a brilliant introduction to a record. But then Adult Jazz are an audacious proposition. Through nine tracks and 51 minutes, their debut album Gist Is, released on the band’s own label Spare Thought, is a voyage that’s startling, mesmerising and magical from start to finish, taking a labyrinthian, fragmented pop-not-pop path, through breathtaking detours, incorporating songs within songs, but very light on its feet and as playful as it is cerebral.

“Slippery and minimal,” was The Fly’s verdict in its top five ‘Ones To Watch’ for 2014. Reviewing ‘Springful/‘Am Gone’, the band’s AA-sided debut single released in January 2014, Stereogum described it as, “quirky and disjointed, yet somehow gliding gracefully through the air.” DIY magazine said, “a mind-bending strain of art-pop that promises to slot them somewhere alongside Wild Beasts and These New Puritans in terms of fantastically British seriousness.”

Whichever adjectives – and there will be many – are used to label Adult Jazz, only one thing is for certain: this music only obeys its own internal logic.

“We don’t see ourselves as having a sound, it’s more aspects that we agree are within the scope of what we do,” ventures singer and spokesperson Harry Burgess on behalf of bandmates Tom Howe, Tim Slater and Steven Wells. “Something melodic and friendly, but with an uncommon character. We like that juxtaposition between, say, something my mother would like, and something she would find difficult! We also don’t feel it’s necessary to tap an idea if we’ve done it once. It means the voices and words are free to be explored and dance around.”

That sense of exploration and freedom defines the sound and vision of Gist Is, from the upbeat, off-the-beat orbit of ‘Am Gone’ to the uncanny, skittering lullaby ‘Pigeon Skulls’, from the surging dig-rhythms of ‘Idiot Mantra’ to the shifting sections over ten entrancing minutes that is ‘Spook’, from “big, slow build to big joyful explosion to a reflective middle, then a massive long grandiose build to an end,” says Harry. On its own, ‘Springful’, appears to transform from blues spiritual to folk-pop to an Afro-tinged passage, which seems to keep the band off-guard as much as the listener. There are myriad samples, sonics that don’t readily admit which instrument made them on, and Harry’s vocal dexterity, judiciously employing falsetto rather than using it as an over-egged default mechanism.

Gist Is also evolved intuitively, taking four years to finish. Studies (and more recently, day jobs) had to be factored in, but the dominant factor was having the freedom, “to write and to realise a direction as we went along. There was no prescribed path for the album, so we could take an internalised approach.”

Enigmatic, non-linear, challenging, fascinating, complex it wouldn’t be ‘Adult Jazz’ if everything was spelt out and instantly understood. The gist is, Gist Is invites the listener to take time to discover its multiple folds, corners and tangents: but what is absolutely certain is a unique proposition, the combination of four audacious and brilliant musical minds.