Sigur Rós seemed to appear out of their own fold of reality, creating epic sounds with a subtle futuristic tint, as if banging out symphonies for a far away jungle: a jungle where the elephants are giant mechanical beasts. Their mixture of classical strings and electronic blips, complimented by the lost-spirit wail of singer Jón Birgisson, must come from a place far removed from the power chords and three-minute ditties of the international phenomenon of pop music.

And like a story with a good ending, Sigur Rós’ three-part audio-visual goodie bag of unreleased tracks, acoustic cuts, and a rockumentary DVD sent the band back “heim” to explore the reverberations of their sounds in their polar homeland.

That being Iceland, where filmmakers had to deal with particulars like avoiding the midnight sun, and finding an evening that would let the world spin into a slant of darkness, but wouldn’t become too cold to play in.

As their manager explains on the film’s Web site, he feared that American filmmakers would “find the clichéd lures of volcanoes, geysers and the Blue Lagoon too irresistible,” insinuating that a postcard-pretty production was less than ideal. Tour-guide beauty would detract from the “annihilatingly huge” quality that humbles spectators as much as it entrances.

Previews dotting the Web promise aurora borealis-colored imagery, and settings gilded with mysticism. The audience appears to play an equally engaging role, even venturing outside the crowd standard of waving lighters and popping Coronas.

Kids lie in the grass and float red kites in the sky, dig in wet black sand, and play soccer in the shallow ocean. The band rehearsals also venture outside the stadium, providing intimate shots of Birgisson strumming to himself, his charmingly crooked teeth bared as he grimaces with concentration.

The transcendent quality which leaks from the film suggests the significance of the first disc’s title, “Hvarf,” which means both “haven” and “disappeared.” As an album of unreleased tracks, the word could rely on both its definitions.

“Í gær,” starts out with soft, foreboding bells, which are abruptly dominated by a wall of guitars, in a glacial wall of sound that injects their regal scores with a tinge of the old garage. The rest of the album takes its time with launching into epiphany, like “Von,” a set of strings that float in harmony like birds flying south, weaving in and out of a melancholy, fit-for-a-funeral mood.

“Heim,” which means “home,” consists of acoustic versions of songs from the band’s older albums. A couple of the songs have a bare, fingers-on-the-strings quality, like the title track from “Ágætis Byrjun,” but most remain above ground, retaining the sense that they are not a thing of nature. Yet what the acoustic versions show is that the splendor of Sigur Rós’ sound is not an effect of a “magic touch” by technology, but organically generated through the regal strings and watery smooth piano of their arrangements.

The discography of Sigur Rós has always had the feel of a musical score for an otherworldly film that would never be made, but maybe we spoke too soon. Soundscapes and landscapes are about to collide, and it looks like they found something other than machinated creatures to speak its lore.