For an artist whose primary emotional touchstones are stillness and serenity, Matthew Cooper refuses to stay in one place for very long.

Right from the start, the ambient composer/producer has taken a departure, slight or striking, with each new release, seemingly making an exercise of finding continually new and different approaches to similar emotional terrain.

Similes, Cooper's fifth full-length as Eluvium, and his first since 2007's sumptuous, symphonic Copia (discounting the like-minded, limited-release “solo album” issued under his birth name in 2008), is no exception: it's his first foray incorporating percussion and vocals.

Hopefully that news hasn't prompted any undue consternation among the Eluvium faithful, though, because this is hardly the shift into beat-driven pop that some might have feared (or, for that matter, anticipated.) The “percussion” takes the form of soft, gentle clicks and pops (and a few distant, barely there thuds) which appear on about half of the album and bear only a casual resemblance to “beats” in the standard sense (save perhaps for “The Motion Makes Me Last,” whose soft, insistent pulse does indeed create a stirring, quietly exuberant sense of motion beneath the prevailing calm.) The vocals, though nearly as unobtrusive and relatively sparse (three of the eight cuts are instrumental), are a striking, almost magical development -– longtime listeners may find the emergence of Cooper’s voice after so many years to be particularly affecting and even revelatory, although it’s as understated an instrument as we might have expected all along: a sober, pensive, near-monotone, whose Ian Curtis echoes are tempered by the baritone richness and introspective, bruised-heart resonance of Lou Barlow and Bill Callahan.

Cooper’s cerebrally abstract, insightful way with language, meanwhile, has long been evident in his well-turned if rather fussy song and album titles.

Those qualities are certainly present in his lyrics, but hearing him intone his own words renders them somehow less ponderous, more yearning and introspective, and gently, wittily self-aware, especially since many of the lyrics here feel like glosses (similes, perhaps?) for the ineffable, absorbingly ruminative experience of listening to Eluvium’s music, or the perhaps not dissimilar sensation of creating it.

And that experience has never been more absorbing, ineffable, or rewarding than it is here.

Despite its innovations, Similes is firmly grounded in the ambient compositional techniques that Cooper has spent his career mastering.

Copia’s lush, variegated organic textures, Accidental Memory in the Case of Death's tenderly tinkling pianos (albeit more heavily processed and ring-modulated than ever before), and even the softly whirring guitars of Lambent Material all turn up here, but the best reference point is the invitingly warm, expansive drones of Talk Amongst the Trees (whose title is referenced in one of this album’s first lyrics) which up until now was arguably Cooper’s zenith.

With Similes, he’s made his most touching, certainly his most engaging work to date, and against the odds, somehow the most quintessentially Eluvium release yet.