Michel Chion’s 1973 composition “Requiem” is a noisy and surreal deconstruction/recreation of the Funeral Mass. In retrospect it sounds positively pre-industrial and is jam packed with grating, annoy-the-dog high pitched frequencies, snatches of actual church music and some genuinely scary uses of the human voice. Listen loudly in the dark if you dare.

from Modern Illusions:

Chion’s Requiem probably represents one of the defining moments of the musique concrete canon, a work all other pieces must be judged by and one of the few absolute masterpieces of the genre. Things begin with a high pitched tone soon joined by an electro-acoustic, echoing wind and then just after 40 seconds, silence, a man narrating a few lines in French and the start of a slow buzzing, chant-like humming, dripping water, echoes, reverbs and more French vocals repeating the words ‘Requiem Aeternam’. And all of this is only two and half minutes into this labyrinthine construction which comes close to nearly annihilating the standard structure of a requiem. Traces of the traditional Funeral Mass remain (largely through the titles of the various movements), but have been so brutally deconstructed that it’s very difficult to know exactly at which point in the proceedings you are experiencing. In fact, it’s almost as if Chion wants to create all moments at once, stopping time so that everything and anything can happen simultaneously, purposefully disorientating and confusing the listener.

listen to the opening piece here
 

 
And here are two more excerpts with great sound quality but not great (mostly lifted) visuals added by the kind fan that uploaded them.