Janacek (1854-1928) has always been one of my favorite composers; really I think it's impossible to find music that he wrote that is not interesting, memorable, and extremely well-written. And, especially in the last few decades of his life, it is hard to find music of Janacek that, happily, is not extremely idiosyncratic, and highly original. Until 1895 he devoted himself mainly to folkloristic research and his early musical output was influenced by contemporaries such as Antonin Dvorak, whom he became friends with in 1874. Early on Janacek composed in a more traditional style, one can find the romanticism of Dvorak never too far away-however as time went by his later, mature works incorporated his earlier studies of national folk music in a modern, highly original synthesis.
I think it's music that Dvorak might have written if- he lived longer and- was a total nutcase. Ok, not really perhaps but my point again is that Janacek's music goes from an early rather conservative style although with a rustic, Moravian/Slovak character..and then we get wonderfully eccentric music based on his prior ethnic musical studies, including his musical assimilation of the rhythm, pitch contour and inflections of normal Czech speech (this helped create the very distinctive vocal melodies of his opera Jenůfa (1904), whose 1916 success in Prague was to be the turning point in his career.) In Jenůfa, Janáček developed and applied the concept of “speech tunes” to build a unique musical and dramatic style, and this too inspired most of his output (his great Operas especially) from that point forward.
His later works are indeed his most celebrated. They include other operas operas (such as Káťa Kabanová and The Cunning Little Vixen), the fantastic "Sinfonietta", the "Glagolitic Mass", the rhapsody "Taras Bulba", "The Fiddler's Child" etc., important choral works, two *perfect* string quartets, instrumental and other chamber works. I adore all of Janacek's music although at times I find myself gravitating to his chamber music most of all. Janacek was one of the greatest Czech composers, but as with much of what I wrote above- I'm pretty sure that most visitors already know this!
There are interesting stories surrounding most of Janacek's piano music, however I doubt people want to keep on reading ;) The Naxos liner notes (pdf) mentions this but not in great detail. Perhaps I'll write about this and "pdf" it in the near future. Enjoy