[I seem to have lost the thread with general quotes about Sibelius and his music, where this probably belongs…]
Here's a nice quote from the composer (of sorts!) Kaihhosru Shapurji Sorabji - a great eccentric! It's really about Medtner but quite illuminating about Sibb as well:
‘Like Sibelius, Medtner does not flout current fashions, he does not even deliberately ignore them, but so intent going his own individual way is he that he is simply unconscious of their very existence... he has made for himself, by the sheer strength of his own personality, that impregnable inner shrine and retreat that only the finest spirits either dare or can inhabit’.
And the Russian philosopher Ivan Ilyin said of Medtner - but might equally well have been speaking of Sibb!: ‘Medtner’s music astonishes and delights… you may fancy that you have heard the melody before… But where, when, from whom, in childhood, in a dream, in delirium? You will scratch your head and strain your memory in vain: you have not heard it anywhere: in human ears it sounds for the first time… And yet it is as though you had long been waiting for it – waiting because you “knew” it, not in sound, but in spirit. For the spiritual content of the melody is universal and primordial… it is as though age-long desires and strivings of our forebears were singing in us; or, as though the eternal melodies we had heard in heaven and preserved in this life as “strange and lovely yearnings” were remembered at last and sung again – chaste and simple.’