I was in Victoria Hall last Thursday for a Sibelius - Henze concert. The Henze was a discovery but I have to admit that Ihave been very early a huge fan of Sibelius whose control of musical form and orchestral colors is just unique.
How accepted is Sibelius even today ? It seems that he is still not that known in Germany and that Rattle has to do some efforts to get a full cycle accepted in Berlin.
Looking at my notes, I first heard the second Symphony with K Penderecki in Paris in 1983 at a concert where I was mostly going to hear Rostropovitch premiere the composer's cell concerto. Two years after in London, I heard the same Symphony with Rattle and the Philharmonia in my encounter with this conductor. Muhai Tang played end 85 the first with the Paris Orchestra and told me that it was the first time the players encountered this piece.
Then I had to wait 1992 to hear Rattle play the same second in London with the LPO followed by Ashkenazy in Boston a few months after. C Telzlaff and Dohnany played the violin concerto in London five years after.
More significant was Salonen and the LAPO toured Europe with a cycle three years ago which allowed to hear the first, third (outstanding work), 6th and 5th ...
(and I cannot I cannot count various encore like the Scene with cranes, a 5 mn max encore played by Rattle and the VPO after a Beethoven 5th in Paris, nor a few Valses Tristes encored with Jansons and the GMYO or P Jaärvi and the VPO ...)
Bottom line, hearing Sibelius in the concert hall is still a rare event. Mahler works are repeated ad nauseam and works are losing freshness whereas fact is that Sibelius remain totally underplayed.