Over the past fifteen years, Primitive Motion, the Meanjin / Brisbane duo of musicians and visual artists Sandra Selig and Leighton Craig, have quietly, consistently, insistently, released a clutch of albums and singles that make good the dream of ‘variations on a theme.’ Their sound, loosely put, is a kind of kaleidoscope, abstract pop that’s webbed between rickety electronics, pulsating Krautrock, airy minimalism, and home-spun drone. If previous albums have focused on particular aspects of the Primitive Motion ‘thing’, with Lost Frequencies they’ve drawn a line in the sand, digging twenty-four songs out from their archives, all played exactly as you hear them, no overdubs, no excess; the moment of creation, unadorned.

An album of this length – over two hours – might read like a magnum opus, at first glance. But listening to Lost Frequencies is an entirely other experience, its relative bareness and fluidity cleaving to the diaristic and the documentarian. Rather than setting out with goal in mind and plan in hand, with Lost Frequencies, Primitive Motion arrive nowhere but land everywhere. The recordings here span almost four years, from December 2017 to November 2021, and they’re collected from the duo’s ongoing improvisatory meetings at Sandra Selig’s studio, Woodburn Laboratory, in Ferny Hills. It’s all first-take material, mostly captured on one mic.

Lost Frequencies moves at its own pace – taken in its full breadth, it’s like one long exhale. While Primitive Motion have hinted at this kind of openness and playfulness before, they’ve never really stretched out quite to this extent on record. But within this, there’s also a curious intimacy, a feeling that as listeners, we’re eavesdropping on a process unfolding. It’s a reminder that blueprints for buildings are often more evocative than the constructions themselves, that sketches offer hints that finished works don’t realise; Lost Frequencies works by inference and through intimation. Someone left a gift on the table, you don’t know who, and you’re not sure it’s for you; this only makes you more curious.

Through Lost Frequencies, Primitive Motion uncover something that’s simultaneously deeply archaic and vitally modern, and while there aren’t too many reference points for what they’re doing, there are maybe a few lines to draw between this music and singular voices like Pascal Comelade, Nico circa Desertshore, Biota, Księżyc, Arthur Russell, Kemialliset Ystävät. There are similarities in sound, sure - the hum of reed organ on “Curiosities of the Sky” or melodica on “Dimensional Fans”, in conjunction with Selig’s levitating voice, are audio madeleines – but Primitive Motion share with these artists, most of all, both devotion to craft, and surety of focus. Over time, a luxury afforded by Lost Frequencies, Primitive Motion take the music elsewhere – which is the only place it really should go.

• Jon Dale