Japan's Mono have been exploring the margins of post-rock since 2006 when they collaborated with World's End Girlfriend on 2006's Palmless Prayer/Mass Murder Refrain, using electronics, strings, chorus, a pianist, and a saxophonist.

2009's Hymn to the Immortal Wind featured large string and wind sections, followed by the live festival performance Holy Ground: NYC Live in collaboration with the Wordless Music Orchestra under the conduction of Jefrey Milarski.

Those albums showcased Mono's sound in transition from its thundering post-rock origins.

For My Parents, again with Milarsky's WMO renamed the Holy Ground Orchestra, nearly completes that move.

Each of Mono's previous experiments with classical instrumentation and arrangements has gone a little deeper and wider.

But these five lengthy tracks move them further toward the edge.

Here they've created a music that seamlessly melds the repetitive, hypnotic, density, and propulsion we've come to expect from post-rock as a genre, yet turns them upside down, focusing increasingly on detail, space, ambience, melody, expansive harmonics, and intervallic architectures.

The more conventional aspects of Mono's sound can be heard in the appropriately named "Nostalgia," where strings eventually give way to quickly strummed chords and open-tuned riffs that gather in intensity, even as tympanis and kit drums thunder up top.

But that's the exception here.

On "Legend," the knot of tension barely rises as the orchestration weighs in perfect balance with the band's more light-fingered touch.

On the glorious "Unseen Harbour," the set's longest cut, elements of restrained dissonance hold sway with meandering yet interlocking melodies, transcendently beautiful orchestral passages, and thrumming rock blasts that alternate throughout, keeping the listener off guard but in rapt attention to a music that approaches pure emotion due to its natural flow and woven dynamics.

"A Quiet Place (Together We Go)" is almost meditative for more than half of its nine-plus minutes.

Fingerpicked electric guitars, shimmering percussion, and a droning bassline are adorned by pastoral cellos and violas that never quite consume the landscape, but hold it in beaming light, provoking feelings of loss, reflection, and tenderness until its close, sending the album off on simultaneous notes of melancholy and majesty.

What's really transpired on For My Parents is that Mono has all but left post-rock behind.

Instead they've become a band whose genre is one of their own design.

Music-making this exquisite is an exercise in commitment, where constant re-examination and ego-lessness become prime motivating forces.

Mono serves its music, rather than making it serve them.

The near perfect balance of cinematic classical and rock music here may put some off some headbangers, but it will no doubt appeal to anyone with an open mind, and more importantly, an open heart.