Since their 2010 self-titled debut, Golden Retriever have distinguished themselves from the crowd of instrumental post-rock and avant-garde experimentalists in no small part due to their unconventional instrumentation. Layering and processing Matt Carlson 's modular synthesizer with Jonathan Sielaff 's bass clarinet, they made a series of albums through 2014's Seer that expanded their sound without expanding their personnel. Three years later, Rotations augments the duo's palette further than ever before with the inclusion of a chamber ensemble on select tracks. Beginning the writing process with compositional fragments and improvisation on the bass clarinet and piano, they built more structured, harmonic motifs and transcribed them for their own instruments, strings, woodwinds, French horn, percussion, and pipe organ. Originally with cyclical improvisation in mind for live, acoustic performances in 2015 that stemmed from an arts grant in Portland, Oregon, they developed the material for their studio project. Reflecting the earlier stages of these works is "A Kind of Leaving," which opens with bass clarinet drone and a repeated piano motif that evolves through repetition. It's one of two tracks that feature only Carlson and Sielaff . Subtle, more frenetic mechanical bleeps add texture and distraction as the bass clarinet, an instrument with a range of over four octaves, slides into the higher melody. The synthesizer eventually takes over the drone before the piece bleeds into the next track, "Tessellation." Its rotating pitch bending on multiple instruments, warbling noise, glitchy electronics, and percussion amalgamate for the impression of a living, traveling mass rather than layers of scored parts. While only involving the duo and a percussionist, "Thirty-Six Strategems" is the most agitated, cacophonous entry in the six-track set. Some of the prior motifs converge on the reflective (in more ways than one) closer "Sunsight," which includes strings, pipe organ, and vibraphone among its timbres. Overall, while the album is varied, it's consistently absorbing as it reveals itself with a sense of suspense through its melancholy ambience. [ was also released on LP.] ~ Marcy Donelson