This disk contains one very important work, a few nice-to-have pieces, and quite a bit of filler that will mainly interest completists, singers and fans of vocal/choral music.
The centerpiece is Ligeti's famous setting of the Lux Aeterna communion that concludes the traditional Latin mass for the dead. Don't confuse this piece with the Requiem (LP4), which is for voices and orchestra and which actually omits this text. Rather, this is a standalone piece for 16 solo voices. Its micropolyphonic texture is very close to that of the Kyrie section from the Requiem, and like that movement, it was featured in 2001: A Space Odyssey. This, along with some contemporaneous works by Penderecki, is the purest expression of 1960s cluster and density music for unaccompanied voices. The performance is great. The London Sinfonietta Voices is a top notch vocal outfit specializing in contemporary music. Their intonation is solid, they can handle the soft entrances in extreme registers, and they're versatile enough to tackle this work's densely knit textures and bass falsettos while still putting on a credible performance of the Hungarian folk songs found elsewhere on the CD. My only quibble with this Lux Aeterna is that I would have personally preferred more reverberation, as this piece is supposed to be very soft and sound "from afar". Cappella Amsterdam's performance on Harmonia Mundi rather fits the bill in this regard.
Also interesting, though a step down from Lux Aeterna, are the three Fantasies after Friedrich Hölderlin, a transitional work that retains some of the style from Ligeti's middle period (especially Le Grand Macabre) but also points toward the more neoclassical tendencies of his late works. The third Fantasy includes a pretty violent setting of the words "Komm du nun" ("come now"). The Fantasies are dated 1982, the same year as the horn trio. The three short Hungarian Etudes came out the following year. These look back to Aventures and are more onomatopoetic than the Hölderlin Fantasies, almost excessively so in their literalism (perhaps Jannequin was a model too). Listeners whose affinity for choral music exceeds mine might find more in these works than I have. My general impression is that Ligeti did much better with either nonsense syllables (e.g., Clocks and Clouds, or Aventures/Nouvelles Aventures) or the rather detached Latin texts of the Requiem than he did with settings of vernacular languages (English, German, Hungarian and Romanian). His mature style so emphasizes tone color, and is so profound in its abstraction and multiplicity of interpretation, that linking it to a concrete text often undermines its essential power.
You get a booklet with Ligeti's program notes and texts and translations. Too bad Sony messed up the index references on the track list (which usually point to the wrong page in the booklet for locating the song texts). A score excerpt from Lux Aeterna would have been a nice touch, of the sort that Teldec supplies with the Ligeti Project single CDs.
Note that the Nonsense Madrigals for six unaccompanied voices are found on LE4.
Ligeti's early works were written while he was living in Hungary under the musical isolation and chafing oppression of Nazism followed by communism. Not surprisingly, most of the music he wrote during this time is dull. There are exceptions to this -- the first string quartet, the cello sonata and parts of Musica Ricercata -- but you won't find them on this CD. Instead, we get a lot of second-rate Bartók, or the sort of didactic, undifferentiated choral music that was written for amateurs throughout the 20th Century. The CD starts with 11 lackluster tracks of this music before you come to Lux Aeterna. Then it's back to Hungarian folksong settings for several more tracks before things get interesting again with the Hölderlin and Weöres settings, at which point another nine tracks of folkloristic music "to be sung rather than listened to" rounds out the CD.
And therein lays the trouble with the completist approach. Not only are these early choral works of inferior quality to Ligeti's later works, they are also stylistically disconnected from them. Lux Aeterna, for instance, is written in an international style that owes nothing to Eastern European folklore. However remarkable it is that the Latin text was set thusly by a Jewish man of Hungarian origin born in a region of Transylvania that's now part of Romania who taught in Hamburg and had Austrian citizenship (despite being more comfortable speaking English or Swedish than German), there's nothing in the music that rules out its being written by, say, a Polish composer or a Greek composer living in France (if you get my drift). Listening to this CD start-to-finish is like listening to those reissued CDs of Broadway musicals where the "extras" are tacked on in the form of deleted numbers, demo tracks, concert fantasies on the song themes, and so on. The material is interesting to us insiders, but my wife, who specializes in musical theater, deplores the letdown of having the show's natural finale immediately followed by an extraneous track that undermines what should be an integral aesthetic experience. This is the essential dilemma of these CDs, to which there's no easy answer, especially when they're organized by ensemble type. I guess I can say that if you're concerned by this, and want to focus only on Ligeti's major works, you might have a look at the Deutsche Grammophon set, in which every piece is an important composition, and where most of Ligeti's greatest music is offered in a concise four-CD collection.
I can't vouch for the Hungarian diction of these performers, but the Latin and German on the disk sounds OK, and you have the benediction of a recording made under Ligeti's supervision.
Note that as of March 2010 Sony has made the entire Ligeti Edition series available in an inexpensive nine-CD box set that includes this CD, so you should probably just buy that set instead of this single CD if you're interested in Ligeti's music.