ALL THE letters and documents presented in this book appear, as far as can be determined, in chronological order. The system of numbering these materials is as follows: All letters and other items from Musorgsky's pen are numbered consecutively throughout the volume; letters by others are given the number of the last preceding Musorgsky item, plus the differentiating letters a, b, etc.; contemporary documents are inserted in their chronological order without numbers.
The dates used in the letters and contemporary documents are those of the Julian calendar, which continued to be used in Russia until after the 1917 revolution, although the Gregorian calendar had long since been adopted by most of Europe.
Marks of elision in Musorgsky's letters are his own, with the exception of those enclosed in brackets. These latter indicate omissions by the editors.
Words enclosed between carets (〈 〉) were crossed out in the original letters.