Collaborative U.K. musician Rozi Plain finished writing her fourth solo album, What a Boost, during a yearlong world tour as bassist for like-minded collective This Is the Kit. The leader of that project, Plain's friend and longtime collaborator Kate Stables, appears on the record, as do guests including but not limited to Sam Amidon, Joel Wästberg (aka sir Was), and members of such experimental groups as Zun Zun Egui and the Comet Is Coming. It's Plain's second consecutive album to be recorded at Total Refreshment Centre, a London club and rehearsal/recording space popular with local jazz musicians at the time, and her intricate, folk-inflected indie rock has a more conspicuous, gentle jazz presence here, including on the improvisational opening track, "Inner Circle." It opens with a slinky guitar riff, spare jazz drum kit, and hand drums, gradually adding additional instruments (electric bass, saxophone, violin, and more). Across the album, Plain's soft, detached vocals are typically double-tracked (artificially or otherwise). Less than a third of "Inner Circle" has vocals, however, as the song closes with a two-minute improvisation that ends as instruments drop out one by one. Arrangements vary from the rolled chords, sustain, and whimsical synth timbres of the more up-tempo "Conditions" to the relatively spare, succinct patterns of "Symmetrical," which relies on piano, contrapuntal guitar, and soft drums. Amid highly processed harmony vocals on the latter, the main vocal line includes abstract lyrics like "Asymmetrical/To be symmetrical/to see symmetrically." Playful and off-balance yet gentle and exquisite throughout, What a Boost closes with a version of Sun Ra's "When There Is No Sun." Along with the cover photo of Plain under gray skies, it underscores the album's suitability as a soundtrack to an overcast Sunday afternoon.