You follow a band you like -- they're not fantastic, but they're good at what they do -- and at some point you think you know what to expect.

And then they drop a bomb.

That's what Balmorhea did with All Is Wild, All Is Silent.

Their previous effort, Rivers Arms, was a sweet and gentle acoustic post-rock affair, with piano, guitar, the occasional violin or bass line.

We are still inside the post-rock ethos with All Is Wild, All Is Silent, but suddenly the group has grown wings and balls! And members too! The once-duet of Michael Muller and Rob Lowe is now a full-fledged sextet also featuring Aisha Burns, Travis Chapman, Nicole Kern, and Taylor Tehan (not sure who does what, but Burns was already guesting on violin on the previous album, and the ear doesn't strain hard to catch banjo, double bass, and percussion).

If the lineup has gained size, so has the cinematic scope of the music: Rivers Arms was all about intimacy (skeletal tunes, simple arrangements), and even the occasional field recording hinted at small spaces (a backyard, a schoolyard), but this CD features expansive music evoking the Canadian Prairies, the American Midwest, or even the wild, rough-edged beauty of Sweden and Iceland (and, yes, comparisons to Sigur Rós are inevitable, welcome, and meant as a compliment).

Right from the start, "Settler" sets the mood with a minor-key melody that reaches symphonic proportions and attains a great level of yearning once the rhythm section comes in.

"Remembrance" has a strong Ennio Morricone flavor, while "Truth" starts like a string-led Sigur Rós piece -- however, Balmorhea's turns out to be more bucolic than that, and the group's brand of post-rock is devoid of noisy/textural electric guitar.

Everything is acoustic and exquisitely arranged, the undisputed highlight of the album being the fortissimo reentry of the piano at the very end of "Truth," immediately switching to a quiet register as it segues into "November 1, 1832," a beautiful tune with wordless vocals performed by guest Jesy Fortino -- that particular passage will be giving you goosebumps for years to come.

Simply put, you can't make instrumental music more beautiful than that.

Highly recommended.