As an introductory post, I figured something rooted in metal would be appropriate, since I will be diverging from that stream pretty frequently later on, so I present to you John Zorn's epic, Jazz Metal non-verbal opera, Astronome. Using the same line up as his earlier release, Moonchild, (in which he managed to persuade a jazz duo to play metal) Zorn crafts an insane three act wordless drama of grim insanity. The concept here is the lack of language, all the vocals are incomprehensible screams, growls, wails, grunts, chokes and basically any other noise you can possibly imagine the human vocal chords producing, and the effect is beyond belief. Quite terrifying at times.
On top of that, the instrumentation, while sounding like metal, is much closer to jazz in its improvisational style. You don't really get repeated riffs, there are themes and motifs but they flit in and out of existence without establishing themselves with any permanence, and the result is a mind-bending randomness that belies a much deeper complexity of form and content. If you like the more out-there forms of metal, noise or jazz music, you should definitely check this one out.