If you write "Night on Bare Mountain", they have to put you in the pantheon of Great Russian Composers. That's the rule. Even if, as in Mussorgsky's case, the author is a nonprofessional composer who worked as a civil servant. He left behind mostly incomplete works, the rough-edged inventiveness of which has inspired acts of "polishing" by an army of admiring composers. In whatever version you hear them, the romantic sweep of "Pictures at an Exhibition" and the majestically impressive opera Boris Godunov are testaments to Mussorgsky's expressive talents.