There is a simplified version of OP. 39, No. 15 in John Thompson's Modern Course Book 1. I started practicing it last year. I enjoyed it very much. But I was not aware of the dialogue between the Major and the minor key. Teacher Andy, thank you so much for pointing that out and explaining the spiritual love in this music!
my personal understanding about Brahms is that he's music is from his thinking, not from his heart (in the sense of Beethoven or Mozart's heart). He learned sharp bright keys from Schumann, only to wrapped it with melancholy from his thinking, like here 13:27. His music, even from the forte episodes 13:41, is so hard to be representative of human emotion like did by classical maesters, but a struggle of an individual. Sorry for speaking so frankly ;-)
