Soliloquy:
The working definition of "contemporary music" has always been music that is similar or identical in compositional form/stylistically comparable to music that is being written at the time; for instance, Boulez' Troisieme Sonate or Bussotti's "Piece for David Tudor 3", while having been written over 50 years ago, would still be considered contemporary due to the fact that aleatoric, textual and visual music is still a current form of composition. Would you say James Joyce's "Finnegans Wake" is not contemporary? How bout Kandinsky's Composition II or Miro's Red Sun?
Do you know what Post-Darmstadt means? =/
In any field of art, "contemporary" has always meant "comparable to current output". Obviously you have to make some discretion with that IE you couldn't say Chopin is contemporary because of the Neo-Romantics. Much of the New Complexity composer Bernd Alois ZImmermann's music pre-dates WWII, and that is certainly contemporary. Many works by Finnissy and Ferneyhough would also not fall into your definition of contemporary.
1) You relate Post-Darmstadt with three different time spans I presented, and ask if I know what it means. Sorry, but what are you talking about? Of course I know what the term means, although - again - I would not say it is precise or definitive.
2) What do you think is "my" definition of contemporary, if I didn't explain it?
3) The definition you present is, sorry to say, old-fashioned. Furthermore, it is absolutely controverse. First, it
was a proper definition until the post-modernism trends, i.e., until mid sixties at best. Since then, it means nothing. Look at (or listen to) the musical panorama we have now-a-days. You have anything happening. You use
your discretion to say that Chopin could not be related to neo or hyper romanticism; then, you use it again to say that Zimmermann is part of neo-complexity. According to your point of view, Chopin is not contemporary and Zimmermann is, despite the fact that both are linked in some way to contemporary music.
Foremost, in the last decade or so, any new work presents an individual collection of "inspirations" and technique, and given the huge number of composer active, it spans from plainchant to neo-complexity, from Beethoven's late quartets to reggae music, and so on. According to your definition, anything is contemporary if you want it to be.
Let me propose that Brahms is contemporary music then. His techniques of composition for sure are part of today craftmanship, as you can notice in both learned and popular music. Glanert made his UK premiere of a piece that uses Brahms's opus 121 as its basis, so his influence is state-of-the-art in music. Why not considering him as a contemporary composer? Ridiculous? Yes, I agree.
4) Your questions about Joyce and Kandinsky confirms to me that you are misundersting the concept of both modern and contemporary music. The two mentioned artists are master examples of what contemporary art was sometime ago, and now is considered modern. They are no longer part of the contemporary world.
5) Just for the sake of curiosity, why do you think that Finnissy or Ferneyhough would not fit in the concept I didn't explain?