Endlessness, Nala Sinephro’s second record, centers on an arpeggio. The London-based composer modulates this ascendant phrase, extends it, plays it more lento, and lets it slip into inaudibility and disappear. It carries us like a rip tide through the album’s 10 tracks, all called “Continuum”—a perfect name for each, though this LP isn’t a series of variations on a single composition. Listen closely, and its details transform at a relentless clip. Let your mind drift, and its 45 minutes resemble a lake: broad, serene, consistent if never flat.

The 28-year-old, raised on the outskirts of Brussels by a Belgian mother and a father with roots in Martinique and Guadeloupe, has both ambient music’s cool breeze and jazz’s strong winds at her back. She emerged as the union of these genres was finally losing its hyphen, during the COVID-marooned days of 2021. Floating Points and Pharoah Sanders’ Promises arrived in March, an event that paired the electronic perfectionist on the same bill as the elder-statesman saxophonist, along with the London Symphony Orchestra. Sinephro’s sparkling debut, Space 1.8, dropped in September of the same year, as though she knew a mantle was waiting to be taken up. She had recorded the disc in 2018 and 2019, but that only made her arrival more uncanny—when was the last time that a couple of jazz records, put out mere months apart, seemed to be talking to each other, disagreeing, finding common ground, and cogitating over a future for the form?

Still, Sinephro scopes out the frontier. Endlessness dissolves the binaries that define ambient jazz and imagines a third sort of music that thrives at their midpoint. Its seamlessness distinguishes Sinephro’s second album from its still excellent predecessor, which was alternately atmospheric and bluesy. This is more cohesive, more elegant. Endlessness merges sensibilities with the naturalness of DNA strands bonding into a double helix. It both proves ambient jazz’s endurance and renders the two terms mutually redundant.

Sinephro has grown considerably as a studio brain and bandleader in the last five years. She produced and mixed every song on Endlessness, engineering them with collaborator Rick David. She also arranged all of the record’s strings—never saccharine or maudlin, they feel poignant and as judicious as any other instrumental feature. Sinephro plays harp, piano, and synths both modular and otherwise alongside a who’s who of friends from South London’s jazz scene. Endlessness’ soul is the energy of the session, the ability of musicians in a room to swap ideas in real time.

The work begins with a tight combo clocking in: Sinephro signals the start with multiple synth parts, Black Midi’s Morgan Simpson adds his drums, and Ezra Collective’s James Mollison jumps in on saxophone. The bandstand expands on the next cut—Endlessness feels auteur-ish thanks not only to Sinephro’s masterminding, but because musicians constantly replace each other, slipping like samples through her deft production. Lyle Barton accompanies on synth, offering a whorling lead part on “Continuum 3”; UK torchbearer Nubya Garcia’s sax sets a spark as “Continuum 5” turns to “Continuum 6”; Dwayne Kilvington lays down sparing synth bass, stabilizing an LP that nearly entirely forgoes any four-stringed foundation; Natcyet Wakili, known for his timekeeping with Sons of Kemet, subs in on percussion; Sheila Maurice-Gray purrs away on flugelhorn and trumpet. Endlessness’ pristine exterior hardly conceals the generative buzz of Sinephro’s players, who give the collection both breadth and persistent gusts of fresh air.

Her easy-come-easy-go ensemble labors against the composer’s production like swimmers battling a current. The pulse she offers at the start soon becomes an invitation to challenge its boundaries. Simpson’s tumbling drumwork rejects the arpeggio only minutes into “Continuum 1,” taking control of duration, stretching it like putty, before he passes it back to Sinephro and the track reorients itself. Meanwhile, synthesizers pluck away like Sinephro’s own harp. The concoction eventually reduces to a sax line so intimate and unadorned that you can hear the pads clack against the brass.

Elsewhere, Sinephro reroutes the pulse herself. “Continuum 7” shifts momentum when she slows the arpeggio, transposes it, and buttresses the ostinato with a descending response to its call. For a glorious moment, we’re suspended as though inside of our own vascular systems, watching as little particles of modular synth and chordophone float by us. The drums lock into the central groove again midway through “Continuum 8” and the group hits its stride, loping forth in jaunty lockstep.

Orchestration blows open the music’s sense of space. “Continuum 2” is a simmering jam turned strange when a noise emanates like vintage technology trying to mimic the sound of a deflating balloon. Then the band loosens, the strings well up; Sinephro’s harp later trickles to the fore, a trip from delicate to robust and back that lingers long after Endlessness concludes. Even when the strings seem to accent the arrangements, as on “Continuum 3,” they move with melodic purpose, their entrances and exits dramatic and without emotional prescription. Endlessness invites us to feel but never tells us what our feelings should be.

The LP has the potential to be a relaxed listen if you welcome this side of its personality, but it’s also vast and complicated. In the dwindling seconds of “Continuum 9,” Mollison sounds a strained note from his tenor. The gesture is fleeting, succinct, and speaks at once to the album’s epic scale and sense of understatement. Sinephro’s music threads a needle between idioms; she makes a garment that both flows with the force of gravity and combats its weight. Endlessness is more than a crafty marvel, or even than the sum of its vaunted parts. It feels like a feat of physics.