Articles about Giacinto Scelsi tend to begin with accounts of his biography and for a good reason: he is a fascinating character, a colorful figure in the tradition of great eccentrics and lonely visionaries, and his life makes for a great story. I will skip it: first, there is a number of articles that tell his story better than I ever could (see Classical.net and medieval.org, as well as an extended and thorough obituary). A second, and more important, reason is that it would have been the wish of Scelsi himself. He was a recluse, granting no interviews and refusing to be photographed - not as a whim, but as a natural extension of his vision of himself and his role in composing:
"Scelsi believed to be a postman, someone who delivered a message, considering himself as a medium between different worlds. [...] Scelsi's unorthodox methods of working proved to be controversial as seemingly questioning the very notion of authorship that even someone like Cage never relinquished." @
"The method used in the pieces for which Scelsi is famous [...] was to improvise extensively on one note and record the results onto tape, this later being transcribed in score by an assistant. Scelsi did not think of these works as compositions with an author in the conventional sense but as snapshots of something more profound and of which the composer was something of an intermediary." @
This approach lead to claims that the music was not, in fact, his, but rather written by his many assistants - although there is an originality and unity of vision behind his output that has to come from one person.
So, if it's all about the music, what is the music like? A common adjective is "monotonous," and it's not derogatory, but directly descriptive. Indeed most of his compositions are based on exploration of a single tone. Yet, the music manages to be engaging, fascinating; it feels like you are hearing a great story told in a foreign language. Scelsi's musical language is completely original and unconventional: completely devoid of melody, yet infinitely rich in timbre, texture, and dynamics; there is no pulse, and rhythm is used only in the most general sense of ideas developing faster or slower; harmony is completely foreign to the classical tradition - it is based on a single note and a multitude of its overtones, so one can occasionally recognize triads and chords, but more often there are microtonal shifts or larger note clusters that may sound dissonant, but not jarringly so.
The entire impression his music makes is like that: dissonant, but not jarringly so; foreign, yet vaguely familiar. His language is not otherworldly, not alien, not futuristic like electronic bleeps and glitches tend to sound. Quite the opposite: Scelsi is reaching into the past, into the history and sometimes prehistory to connect to the deepest human musical impulses. This is how Scelsi himself saw his music: the composition titles are in Latin, Sanskrit, Sumerian; they refer to characters and concepts from Near Eastern, Mayan, or ancient Greek mythology.
My personal aural association is different; once upon a time I read an article on diddley bow - a one-string homemade instrument played with a slide - which said that in early African-American folk music there tends to be little use for pure timbre, and homemade instruments are often augmented with buzzers and rattlers attached to the string to dirty up and fuzzify the sound. The Afro-American folk tradition was completely unknown to Scelsi, yet again they seem to produce convergent results.
To connect to another previous idea, while Scelsi was not an orthodox believer like Pärt or Bach, he definitely was a mystic and saw his work in spiritual terms; music for him is something external to and something greater than a man; and I think that his attempts to remove his ego from the process of composition improve results dramatically.
See also essays on AION and Konx-Om-Pax.
Links: the source, AION / PFHAT / KNOX-OM-PAX on depositfiles
A three-CD collection of his Œuvres Pour Chœur Et Orchestre (including the material on the disc above) at uaxuctum (incidentally, the blog is named after a Scelsi composition)