Some words should be said about the various versions of this work. Zemlinsky's "Der Zwerg" has been recorded before in a different version by Gerd Albrecht, but under the name "Der Geburtstag der Infanta" - and then in a cut (to fit on one disc) and revised version. For the 1981 staging, that proved to be something of a revival of this marvelous work, Adolf Dresen revised the libretto to fit Oscar Wilde's original story more closely. In fact, the cuts don't constitute the main difference - rather, the title character was altered from the pitiful, delusioned but noble character of Zemlinsky's original (used here) to a sniveling creature, mad, still pitiful but without the noble, aristocratic streak Zemlinsky and his librettist gave him. The difference is actually quite important to the story and its inherent symbolism (the dwarf in this version was conceived by Zemlinsky as at least partially self-biographical). I am not claiming that the revision is in any way inferior in itself, but the original fits Zemlinsky's music better; subtle traces of leitmotifs, and certain parts of the musical imagery, for instance, make much more sense here than in Albrecht's version.
In any case, this is an absolutely marvelous work; the musical language is opulently late romantic with shimmering textures and soaring vocal lines, but with an intense twilit atmosphere, full of yearning and magically fairy-talish. Performance-wise there is less to choose between the versions than the differences in story and text could suggest, although the new set is, in the end, overall superior. Conlon's cast is overall stronger, for instance, but then apart from the dwarf himself - David Kuebler's performance is very good, poetic and lyrical but Kenneth Riegel's dwarf for Albrecht has (despite the revisions to the text) a certain sympathetic nobility to him that is quite compelling. Isokoski is, however, a gorgeous Infanta, wonderfully sung and characterized.
The lesser roles are also very good (even though there are several names here I am barely familiar with or not at all), but the main attraction of this set as compared to its predecessor is the sumptuousness of the orchestral sound; the Cologne players play with a burnished, rich tone, exhibiting a wide range of colors and shadings and attaining some gorgeously rich orchestral textures. In fact, I can hardly imagine a more evocative, lushly atmospheric performance. The sound is excellent as well and the musical experience as a whole quite ravishing. Urgently recommended, and for all the virtues of the Albrecht set, this is probably the one to have.