Over the course of eight releases, Portland duo Golden Retriever has plumbed the depths of what two seemingly incongruous instruments can do. Matt Carlson’s modular synthesizer and Jonathan Sielaff’s amplified/effected bass clarinet are like loners at an observatory, gazing at constellations, not quite separate but not really together either. Their catalogue has stayed on that singular track. To accuse Golden Retriever of repeating themselves is missing the point. It’s more like they’re picking up where they left off in a thought stream of audio.

Rotations, the duo’s ninth release, is an intriguing development. What started as improvisations between bass clarinet and piano led to collaborating with a chamber ensemble, featuring the likes of violin, viola, French horn, cello, vibraphone, alto flute, oboe, pipe organ and percussion. The recordings of the ensemble were then deliberately arranged by the two for further cohesion. In recruiting additional musicians, Golden Retriever are less focused on giving orchestral instruments their individual moment in the sun and more focused on layering their existing sound further and further, as if to reassert its capabilities.

Seemingly by design, there are few standout moments for any instrument on Rotations. Aside from the modular synth and bass clarinet, the only one that shows any dominance here (relatively speaking) is the piano, which trembles as a wall of synth expands and woodwinds swirl around it on opener ‘Pelagic Tremor’. On ‘A Kind of Leaving’, a delicate, repeating melody proves to be the ideal counterpoint to the bass clarinet, which enters the seven-and-a-half minute track with weary resignation but with enough time (and a few swells) shows some glimmer of hope. The notes fall erratically, yet John Savage’s alto flute makes it seem graceful by proxy on ‘Thread of Light’. Closer ‘Sunsight’ is arguably the closest Golden Retriever has ever gotten to a weeper. Sparse piano notes initially decorate the arrangement. Then, strings enter for support before Sielaff’s bass clarinet enters like a messiah. Make no mistake, the most sentimental it gets is a few crescendos and thumps of drum towards the end. But it’s still striking for a duo whose previous efforts seemed more focused on sonics than progressions.

On this six-track album, the middle two tracks are the strangest and incidentally, the strongest. ‘Tessellation’ is a shimmering wave of synth and pipe organ in which the bass clarinet is less about providing accompaniment and more about just keeping the arrangement afloat. Yet it all comes together in earned ethereality. The reverb-smeared ‘Thirty-Six Stratagems’ is like a harsh noise carnival, with buzzing and frantic synth, feedback, clattering percussion and sounds that are positively bouncy but signify anything but joy.

Occasionally, Carlson and Sielaff lose control of their arrangements or let them just peter out. Other times, like on ‘A Kind of Leaving’ and ‘Thread of Light’, the beauty is a bit too surface level and needs some element of hypnotic curiosity to heighten the listening experience. The chamber ensemble expanded the possibilities for them immensely, but it’s unnecessarily timid at times. Overall, though, Rotations is a successful venture from a duo who have carved a niche but refuse to just whittle mindlessly.