Reading this wikipedia entry on Rachmaninoff's fourth concerto makes we want to read a biography. It is worth the read - very interesting.
I know that saying Rachmaninoff had a dark horse in his oeuvre is kind of like saying that Andrei Tarkovsky had a masterpiece in his. So while I think there is something dark horse about all of Rachmaninoff's music, there is something especially dark horse about his fourth concerto. But as his pieces are also frequently masterpieces, his fourth is in my opinion the best of his concertos.
It's not that I'm just a sucker for dark horses (I am) but what is in fact initially dark horse is actually that magnanimity; that expansiveness-from-inwardness carrying an internal logic; that generosity which doesn't care about showing off, but would rather have your ear as collaborator in listening; that special quality of Rachmaninoff that has pleased me so much since listening to his work with some semblance of attention (not the studied sort).
I simply cannot understand the ridiculous viciousness of some of his critics back in the day. Were they so glutted with the repertoire of the intelligentsia that they were rendered totally deaf and stupid and robbed of all sensibility and sensitivity?
From comments I've read, some people say that Rachmaninoff was insecure, and it was this that led him to constantly revisit his fourth, cutting it down each time. I don't know anything about his life, but I wonder if it was rather that the same receptive sensitivity that gave birth to his music was also the same sensitivity that rendered him particularly vulnerable to criticism. A blessing and a curse.
My first hearing of the fourth concerto was - as with most - the "final" version. I loved it then and still love it, but when I listened to the original I was quietly gobsmacked. What was wrong with it?! It was perfect! As one commenter wrote on youtube, "it breathes". Indeed.
Nonetheless, I love both; I love how it emerges whole-cloth. Just listen to that opening! I thank God for such music. Rachmaninoff's music suits me down to my bones.
And here is the original (it bugs me that the person posted it in parts according to movements - meh):