This is the question renowed Peter Maxwell Davies posed in recent Royal Philharmonic lecture. The full run-down is nicely covered over at the always engaged blog "On An Overgrown Path" (which, btw, is the title of one Janacek's best piano works).
Sir Davies' lecture can be found here. Read more about it here On an Overgrown Path.
And while surfing about, check out this fine recording of the Janacek work.
Link - amazon