host have been haunting (sorry, but it is the best word) the psychedelic underground since 1986. Ever since their classic self-titled 1990 debut full-length, this Japanese collective have developed into one of the most important advocates of deep head muzik. Basically, Ghost were Terrastock material way before Terrastock was a fixture on the drone-rock landscape.

Over the course of six albums (including the live set, Temple Stone), Ghost’s music has moved from pastoral British folk to the mantric-satori drone rituals of ‘70s Japanese collective Taj-Mahal Travellers to acid-spiked Buddhist temple services to the tribal percussion/ecstatic chant jams Amon Düül I ground out in the late ‘60s. Led by guitarist/vocalist Masaki Batoh Ghost find strength in fragility, a typically Zen achievement for this very Zen-like outfit. Now, nearly five years after Ghost’s last recordings—the one-two punch of Snuffbox Immanence and Tune In, Turn On, Free Tibet—the group return with their strongest effort since 1996’s Lamarabirabi.

To generalize, Hypnotic Underworld is Ghost’s prog-rock move. While still solidly rooted in ancient folk modes, thanks to liberal use of archaic tools like bouzouki, tin whistle, Celtic harp, and bells, this disc promenades down some particularly fruity paths that recall prog’s florid excesses. (A cover of Dutch cult faves Earth & Fire’s delicately beautiful “Hazy Paradise” hints at Ghost’s approach on Hypnotic Underworld, as Batoh falsettos over dewy electric-guitar riffs and Mellotron oscillations.)

Album opener “God Took A Picture Of His Illness On This Ground” (actually the first movement of the four-part title track) may mislead listeners into thinking they’ve stumbled into one of Taj-Mahal Travellers’ soul-shaking concerts by the sea. Ghost conjure a sparse atmosphere constructed of squealing guitar feedback, sluggish bass, Celtic harp strokes, wistful recorder, bells, twittering Korg synth, ululating sax, and slowly rumbling drums. The gradual accrual of sonic elements coalesces into an eerie overture that foretells many mysterious passages to come. It’s the kind of centipede-paced scene-setting that’ll separate the true heads from the avant-rock dilettantes.

Things pick up with “Escaped And Lost Down In Medina,” as a serpentine bass line and sinuous recorder waft over rapid, Cecil Taylor-esque piano runs and downtempo rimshots, and “Aramaic Barbarous Dawn”’s gnarled power chords (courtesy of Michio Kurihara’s guitar) and a chorale of “ooohhhh”s. Unfortunately, Batoh dampens the excitement with his trademark flat voice (if anyone ever needed reverb and other effects on his pipes, it’s Batoh). The title suite concludes with an infernal 20-second Ruins-like acceleration into oblivion aptly titled “Leave The World!”

Hypnotic Underworld’s second half begins the prog-rock odyssey with the aforementioned “Hazy Paradise,” and then dips a dainty toe into the idyllic folk of “Kiseichukan Nite.” The band’s supremely fragile instrumentation, Batoh’s whisper, and dripping water, transport you to a first-millennium teahouse; only a hypnotic bass line worthy of Cecil McBee indicates this is a modern recording. The album’s next four songs roam from mellow bliss outs to storming Jethro Tull-like waltz rock to ballads full of Pink Floydian pomp to rambling Druid ceremonies enacted with bouzouki, tin whistle, and typical rock instrumentation.

Ghost finish this peculiar opus with a rendition of Syd Barrett’s “Dominoes—Celebration For The Gray Days,” off his self-titled solo debut. Barrett’s morose, slurred waltz is an ideal vehicle with which Ghost to ride into the sunset. The group transforms the original into a hazy ballad with flute, slide-guitar sighs, and twinkling keyboards. Then a door slams and an organ fibrillates to fill a hypothetical cathedral with what could be Charlemagne Palestine’s holy chords. Batoh’s voice gets filtered through a Leslie speaker, an acoustic guitar chugs, bells toll, and Barrett’s original is but a distant memory.

As sumptuous and sublime as much of Hypnotic Underworld is, Ghost tend to noodle too long, even for long-attention-spanned folks like your reviewer. (And while we’re carping, Batoh is sometimes prone to melodramatic wailing his drab monotone can’t support.) Still, I’d rather hear Ghost’s overreaching ambition and exploratory excess than the stunted machinations of most current indie rock.