Samuïl Feinberg. Who still knows him? Once a world-famous piano virtuoso, he was the first in the USSR to perform Bach’s complete ‘Well-Tempered Clavier’. As a composer he was also quite famous in his time and that despite the travel ban.
In total, Feinberg wrote twelve piano sonatas, all composed between 1915 and 1923. And all of them were performed and published at that time. With one exception: the third. The composer himself prevented its publication. Why? According to Nicolo-Alexander Figowy (himself a pianist and a Feinberg expert, who provided us with all the important insider information in the accompanying textbook) Feinberg thought his composition went a bit too far. He thought the world was not yet ready for it.
Personally, I do not find his third sonata less approachable than the other five. None of them are easy pieces that you can just absorb; they all require the listener to pay some very concentrated attention.
And you need a really good performer to make that happen. I can think of no better ‘guide’ than the Canadian master pianist Marc-André Hamelin, who is one of the greatest advocates of unknown repertoire, forgotten works and their creators. His playing is unequalled in its grandeur. It is not easy music, you really have to make an effort, but the effort pays off.