Also Mussorgksy I came to know around the time when a friend of mine gave me the biography of Galina Vishnevskaya. If it was because of the book I can't remember, as I was then in the "Russian" phase. (My second one)
Once Ihad the film produced by Nupend about Ashkenazy, where he performed the piano version and the original orchestral version and was interviewed at the same time; Alas videos are out of date!
Anyway here a piano version by Ashkenazy in three parts.
Here a orchestral version.