Australia's Alchemist are a true rarity among metal bands.

In a genre where six-strings rule supreme, keyboards and synths have always been viewed with extreme caution, and rightly so, since historically most of their contributions to heavy metal have resulted from ulterior motives of overcommercialization and, hence, are counterproductive to the genre's uncompromising tenets as an underground movement.

Still, in rare instances over decades past, a few bands, like Rush and Faith No More, have integrated keyboards with very positive results and without corrupting their sound, usually because these merely accentuate and never overwhelm the final product.

Alchemist fall into that category.

Their fourth album, 2000's Organasm (only released in the U.S.

the following year) is so complex and original that it defies a summary definition, but one might describe it as a psychedelic-prog-soundtrack-death metal album.

With its unorthodox splicing of musical styles, opener "Astral Spectrum" (introduced, fittingly enough, by a didgeridoo) quickly sets the album's experimental tone, fusing a thunderous rhythmic hotbed of sub-thrash guitars with atmospheric keyboards taking the shape of flutelike nuances.

Add to this singer Adam Agius' interchangeably clean and death-style grunted vocals (not to mention the most terrifying shriek this side of Roger Waters), and the overall effect is akin to Entombed wrestling with Pink Floyd.

The ensuing "Evolution" trilogy, more than anything else on the album, evokes memories of vintage Rush, largely because of its lyrics, which pursue that Neil Peart-patented clinical/scientific/esoteric approach.

Organasm also scores points for being an "album" in the classic sense, consistent throughout and leaving many of its biggest surprises for the latter part of the set (an increasing rarity in the post two-sided vinyl CD era).

Witness the Cinemascope buildup and angelic/demonic choral vocals of the astounding "Tide in, Mind Out," or the even more surprising "Eclectic," which opens with a spiraling guitar figure straight out of Faith/"Primary"-era Cure before exploding into a furious thrash-out.

Best of all, no matter how extensive their experimentation, one thing remains constant throughout Organasm: Alchemist are always unapologetically heavy.

Highly recommended.