Ligeti, Messiaen, Penderecki and so on.

There doesn't seem to be much by way of Neue Musik in the archived threads. Shall we get one going on this contemporary niche?

Comments/sugg'ns re literature, interpretations or just stuff from bookmark files etc. are all welcome. A first post will follow shortly.
Here are some websites with sample listening material that provide a nice introduction to - and focus on - specific composers:

Karlheinz Stockhausen - Stockhausen-Verlag, media files

György Ligeti - Tonbeispiele (music samples)

Isang Yun - Uni Mozarteum Salzburg (samples, discourse) (German)
Try buying a copy of the Gramophone Classical Good CD Guide and reading it :-) This is not just like reading the telephone book. Many of Gramophone's editors are musicologists, and the discussions under any given composer's work often describe the style as well as the recordings available. I've found a surprising amount of good music this way.

Also, I enjoy having reference books that can occasionally supply some context around styles. One such tome is Robert P. Morgan's "Twentieth Century Music" (Norton, 1991) but I'm sure there are others if you rummage through Borders or Barnes and Noble. Eggheaded, I know.
I have one original Stockhausen LP, cannot find it right now but I think it is four orchestras and youth choir.

I believe his work was influenced by Edgar Varese. I have two Varese, both conducted by Robert Craft. I bought these on Columbia LP, released in 1962. The first is "Ionisation and Poem Electronique" (MS6146). The second, Arcana / Deserts / Offrandes with Columbia Orchestra (MS6362).

This material is so abstract that I was not shocked when Jimi Hendrix released "EXP."
Varese also influenced Paul McCartney and Frank Zappa.
Bienvenue cher confrères!

To Flex' book rec'n --coming in at 1,376pp (!) in its 2003 edition-- I'll add, for general purposes here, any of C. Rosen's writings on music, especially the slim & succinct monograph of '75.

One of the questions that often arises with regard to "new music" is - Who do you mean? In any case here are a number of composers for the categories Atonality, Electronic Music, Integral Serialism, Just Intonation, Microtonal Intonation, Minimalism, The New York School and Twelve-Tone from Mozilla's Open Directory Project (ODP), dmoz.

A couple of links to general sites where some of their music can be heard will be posted later :=)
In the same vein as the first post -but generally (not restricted to the contemporary)- visit also, Classical Plus, Composers (Birtwistle, Lutoslawski, ...-astonishing site :0), CD Catalogue (Berg, Shostakovich,...)

Classical Music Archives, artists' index
Why doesn't Elliot Carter get the recognition he deserves?
Who is Elliot Carter?
Elli-ot, Elli-ot, ... - Say, wasn't that ET's little friend?

Carter ex.'s -- Symphonia/Clarinet Concerto, GRA f. B flat clarinet, Sonata f. Cello
Cher Agonanon...

My (poor) contribution: Segerstam and Taverner, the latter of courtse offering new approaches to old music (byzantine).

Interesting nonetheless, ditto Seger, especially the latest pieces.
Ligeti. 1st and 2nd String Quartets
Schnittke. 1-6 Concerto Grosso; 1-8 Symphony; Piano Quintet
and Piano Trio
Webern: all the instrumental pieces; the lied are very hard
to take (hard to believe but some of his works are almost
100years old now!)
Berg: if you like opera try Wozzeck; Lulu is ok
Bartok: his six string quartets IMHO are the creme de creme
of the 20th century, some are more freely chromatic than
A. Part: highly emotive mystical tone poems

What do you think of Philip Glass? I am not sure if I do but I have his Glassworks CD. Reminds of a repetitive 3 chords garage band song. Over and Over and Over.......

BTW: I can only play most Modern Music when my wife is away.
She hates the stuff. She says if she had to listen to it
she would kill herself in about an hour.....
I have not been partial to Glass fearing the jokes may not be entirely untrue, will have to investigate further... For her may I rec'd Messiaen's rhapsodically tranquil Vingt Regards sur l'Enfant-Jésus? It comes with a guarantee of longevity ;-)

Mais enchanté toujours, cher Gregm!

Esteemed Albertporter, Zaikesman, I was not aware of Edgar Varèse and am now finding him congenial - thank you...

EV excerpts:
Integrales f. small orchestra and percussion
Ofrandes: Chanson de la haut f. soprano and chamber orchestra
Ofrandes: La croix du sud f. soprano and chamber orchestra
Density for flute

Por todos los Zappatistas, EV: The Idol of My Youth
There have been so many style progressions in the 20th century. A few favorites of mine:

-Berg String Qt. and Lyric Suite for String Qt. (by the Alban Berg Qt.)
-Lutoslawski String Qt. (by the Alban Berg Qt)
-for other string quartets contemporary with Bartok but not similar in style, the quartets of Shostakovitch (Emerson Qt) and Zemlinsky (Artis Qt)

And if you like orchestral work,
- Lutoslawski's Mi Parti and Musique Funebre
- most of the orchestral works of Thomas Ades
- the idiosyncratic and non-atonal works of Rautavaara, such as Cantus Arcticus
- John Tavener's Lamentations and Praises, sung by Chanticleer. Tavener has been progressing away from strict minimalism and combining other elements, as Gregm says
Lately, I have been listening to John Adams - Naive and Sentimental Music. It has an enormous dynamic range and is interspersed with quiet, contemplative, and ambient sections. I think one could compare the essence of nature invoked in some passages with parts of the Sibelius Tone Poems released recently on Naxos. Unlike some modern music, this Adams recording can be listened to with other people in the house (but watch the volume on the percussive accents!).
Flex: I am very grateful for your kind recommendations and specificity. I feel very much that -certainly as regards contemporary classical- our musical tastes significantly overlap (but you are much further along). Thank you for the benefit of your knowledge. Rautavaara- wow!

(For anyone interested, some quicklinks to bkgrnd, etc after some of the above rec'ns & contribs to be posted later.)

Incidentally, among my favorites are also the Str Q of Shostakovich - + Kurtág's
Music for Strings... for choral work Ligeti... I lament that more chamber works like Schoenberg's Kammersymphonie N 2 Op.38 are not easy to find. I also like the compactness of Berg & Webern's shorter works (e.g. Berg's 3 Pieces for Orchestra). Reaching further back, even the understatement of some of Bach's Orgel-Büchlein seem an interesting precursor of minimalism.
Agon, thank you for your kind words. I have been learning from this thread too...out hunting for more Schnittke and Segerstam. Exchange of music is one of the best aspects of Audiogon.
Indeed, and I hope others will continue to post comments, etc. re new music on the board - but I have to go shopping now too...

Schubert's Sym N 8 - also known as "Die Unvollendete"/"Unfinished".
Neue Musik - an incomplete blog based on music mentions in this thread.
Agonanon: Ah! Schubert's No.8.......For something a little
off the beaten path, try a recreated No.7 and No.10. Both
are from part scores that were orchestrated by Berbould.
The No.10's second movement(only 3), was almost Mahlerian
in sublimity, shows where the composer was headed.

New/Art Music: Berio's Voci II, Kim Kashashian, viola.
ECM New Series. Hard to understand, and at times extremely
dissonant, but worth pursuing if you like Kim's viola
playing (which I do, she plays Brahms' Opus 120, clarinet/
viola sonatas, with a rich, warm tone)
Schubertmaniac, thanks for the Voci II recommendation, I didn't know there was a 2nd volume out!

Kim Kashkashian has also done most of the Giya Kancheli series on ECM, along with a Schnittke concerto, all of which I enjoy very much. Manfred Eicher seems to keep pulling in extraordinary players, like Rostropovitch, Kashkashian, and Gidon Kremer (not to mention his whole contemporary jazz roster, which belongs in another thread).