At first blush, there’s something surprisingly direct about the latest Built to Spill album. It includes a song called “C.R.E.B.”, an acronym that stands for “cAMP response element-binding protein” — a cellular transcription factor, a microscopic building block of human life that’s essential to the formation of memory and neuroplasticity. While frontman Doug Martsch has always been concerned with the essential elements of human existence, it’s strange to see him dig straight into the physical brain rather than the worlds it builds, explores, and remembers. Maybe it was just an excuse to use the word “hippocampus” in a noir groove. Though it’s Built to Spill’s first album since 2009’s There Is No Enemy and it features a new lineup, Untethered Moon sits right at the band’s musical sweet spot: tight webs of guitar, knotty at places and dangling in the breeze elsewhere. But that reduction to the physical belies the melancholic streak in Martsch’s evocative phrases.