The cinematic vision of German born film-maker Werner Herzog has long been a great influence on the work of dark Italian prog band Il Ballo delle Castagne. Paying homage to the director, `Soundtrack for an Unreleased Herzog Movie' is the fourth studio album from Vinz Aquarian's RPI group, arriving only a few weeks after their `Live Studio' performance, and it is their most lavish, diverse and multi-faceted work to date. Compiled and worked on from demos originating from various recording sessions for their past couple of albums, `Soundtrack...' incorporates more Middle-Eastern sounds than ever before from the band, with a rich concoction of space, psychedelic and gothic rock and even classical fancy that is still frequently identifiable as proper daring RPI. This sumptuous work offers a greater depth and complexity only hinted at on their previous albums, and never before have they released something so mature and varied as this gorgeous, exotic and darkly ambient work.

Ethereal gothic siren cries call through echoing crystalline caverns of the opening track `In the Garden of Popul Vuh', with spiralling dreamy harpsichord, drowsy horn and fragmented piano bursts in the final moments. The piece almost calls to mind Antonio Bartoccetti's Antonius Rex with its eerily seductive and uneasy dream-like atmosphere. Even better is the evocative mix of sounds throughout the highly disorientating and hallucinogenic instrumental `Lentus in Umbra'. Wavering psychedelic synths spin around wild harpsichord, a sporadic pulsing beat, low-key organ, gentle earthy hand percussion and thoughtful yet spirited acoustic guitar runs. Sweeter, almost romantic themes gradually reveal themselves along with a mix of regal and medieval flavours, and it covers many sides of the classic pure RPI sounds.

The dark spirit of Jacula and Il Babau & I Maledetti Cretini haunts `Il Pianto di Cristo su Gerusalemme'. Vinz's raspy narration frantically croons over Il Segno del Comando's Diego Banchero's murky bass, ruminating one moment then heading straight to the skies of space-rock heaven the next. Wailing voices courtesy of female singer Maetheylia, also from the last Comando album `Il Volto Verde', hisses, electric guitar distortion groans and droning sitar weave around harsh electronic slices and lustful electric guitar burnings, all growing in intensity as the piece climaxes.

Eastern themes ripple through the second side's `Profumi D'Oreinte', a brooding dark folk piece that is actually quite an accessible tune, yet still implements plenty of lavish instrumental character. Dark synths, sombre acoustic guitar and a breathy unearthly vocal over rattlesnake-like percussion form the piece, with careful washes of scratchy Mellotron wisps and some stirring electric guitar soloing from Roberto Lucanato in the later half. Ten minute album closer `Sicut in Caeloo' displays the most restraint and supreme taste of all. After a gloomy narration gets out of the way, the track solely becomes a ghostly melancholic classical piano piece full of moody drama and great subtlety, a true showcase for Marco. It's as equally darkly thoughtful and exquisitely beautiful as it is haunting , and it's a very stark yet confident way to end a most unexpected of albums.

Despite several solid albums already in their discography, `Soundtrack for an Unreleased Herzog Movie' is truly Il Ballo delle Castagne's boldest, most sophisticated and defining musical statement to date. 2015 may have already offered several standout Italian progressive releases, but this sounds like nothing else entirely, and it could be a real kick up the ass to ignorant listeners under the impression that all RPI albums are bombastic keyboard-driven symphonic prog. Italian progressive aficionados absolutely need to investigate this wickedly addictive, exquisite collection that hides buried deep within that spicy hint of danger that inhabits all the best Italian progressive albums, and the band have delivered not only a career best work, but one of the strongest Italian releases so far in 2015. Go on, take a walk on the dark side with Il Ballo delle Castagne.

Five stars.