Not sure about the music on this particular disc, but yes, in general, Finnissy can very fairly be bracketed with Ferneyhough et al, at least in terms of complexity and difficulty. Comparing like with like, his piano works, at their most complex, way exceed in difficulty Ferneyhough's piano music - Ferneyhough's own analysis of Finnissy's outrageously, obscenely complex early Song 9 is a classic; but there are plenty of other pieces, small and large, in the Finnissy canon, that challenge it - it's not a surprise, as Finnissy was one of the first and one of the best specialist pianists in this repertoire, and still is. That ought not to be important, I suppose, but it is fair to get the measure of the man.
I've seen dozens and dozens of Finnissy scores, from his juvenilia up to some of his most recent stuff, and I've never come across anything resembling improv - it is always fantastically detailed, richly illuminated and hugely expressive stuff; there are pieces which involve complete dislocation between the written parts, but the parts themselves are always written out in full.
Cards on the table, Finnissy is, for my money, the most subtle, communicative and individual of the complexity bunch, if they can be grouped together at all any more. Whether they can or not, Finnissy is, IMO, perhaps the composer who transcends any suggestion of a complexity clique more than any other. He is, quite apart from any issues of complexity, a really, really fine, impressive composer, one who I count amongst the most important and overlooked of contemporary music, and one whose music may well last a long time (like other piano-specialist composers in this, I guess - an unglamourous niche but one whose potency tends to be revealed slowly - stand up Alkan, stand up Busoni). He has a personal tone, a kind of aesthetic, such as I associate much more readily with the great romantic pianist-composers - think of the diary-like intimacy and individuality of Chopin compared to Liszt compared to Alkan compared to Busoni compared to Sorabji - Finissy fits right smack in the middle of that line. The heart of his music is for piano - his Verdi studies, his ravishing Gershwin studies, Folklore, English Country Tunes - but also smaller piece of rare poetry, particularly his paraphrases on other musics, Irish folksongs, barrelhouse blues, Australian sea shanties, aboriginal music, Dunstable, Bach, Debussy, Mozart, Rossini, Johan Strauss, Bizet, Sullivan (oh my word, his traversal of 'The Sun Whose Rays' sends shivers through me...) and, my favourite piece of his, Berlioz - his paraphrase of the scene d'amour from Romeo et Juliette, Romeo and Juliet are Drowning, in which the original is sumberged beneath gentle suffocating waves of counterpoint.
Outside this, though, his intrumental music is often of great beauty - I'd recommend Red Earth, a kind of Tapiola for the outback, or Traum des Sangers, a delicate tracery of sound inspired by Caspar David Friedrich - both on NMC, though not necessarily easily....
