Finland's Swallow the Sun are well known among extreme music fans for their uncompromising musical vision and ambition.

Songs from the North I, II & III, a 21-song, two-and-a-half-hour triple album of all new material offers proof.

Each disc is a separate album, though all were conceived, written, and recorded as a single project with the band exploring different aspects of its sound.

What unites them musically is a pervasive melodic sensibility, no matter the setting.

Lyrically, themes of grief, loss, and despair run throughout, but the natural world -- wild, mythical, spiritual -- bears unflinching witness and is the glue.

Disc one extends the terrain explored on 2012's Emerald Forest and the Blackbird.

Eight songs offer richly textured arrangements balanced between acoustic and electric instruments amid alternating clean and dirty vocals.

Usually commencing subtly and gently, these tracks eventually build toward shattering climaxes.

"Heartstrings Shattering," featuring a return appearance by Aleah Stainbridge (Trees Of Eternity) is prime STS.

Fingerpicked, echo-laden guitars give way to a gothic pop melody, fueled by massive drums and razor-sharp riffing behind the male and female singing.

"10 Silver Bullets" is darker, more unhinged, and sinister, while the neo-classical dramatic frame on "From Happiness to Dust" is no less punishing.

On disc two, STS play almost completely acoustic with clean singing.

This album's songs bridge the set with a haunted, near ethereal atmosphere, but the lack of volatility makes the sadness more pronounced.

"Pray for the Winds to Come" uses 12-string acoustic guitars, cellos, electric bass, and subtle keyboard shades behind a desolate vocal from Mikko Kotamaki.

"The Heart of a Cold White Land," played in waltz time, offers striking fingerpicked acoustic guitars, highlighted by bells, chimes, and strings.

"Before the Summer Dies" weaves electric and acoustic guitars, a pulsing bassline, swinging drums, and elegantly stacked vocal harmonies.

The final disc offers the biggest, meanest, and darkest surprise.

This is the first time that STS have indulged in bruising funereal doom with such extended, violent concentration.

The shortest of these five songs is nine minutes.

At 13 minutes, "The Gathering of the Black Moths" is as low, slow, menacing, and brutal as any Sunn 0))) track, but it's far more musical.

Deep, resonant, ceremonial brass instruments, horrific guttural and screamed vocals, a shattering, detuned bassline, black tremolo picking, and martial processional drumming enter the track.

It then shifts to include melodic breakdowns and death metal interludes before returning.

The brutally beautiful "Empires of Loneliness" features guest narration from Daylight Dies' Nathan Ellis.

Drummer Juuso Raatikainen's tribal drumming, chanted Gregorian-esque choruses, psychedelic guitar effects, waves of keyboard washes, and rumbling bass erect a wall of sonic dread that cracks open during a blackened death metal finale.

Releasing Songs from the North I, II & III demonstrates a radical belief in the physical concept of the album -- an act of defiance in this age.

While each disc stands on its own, it's the sum total that makes this such a career-defining work.