In a letter to Nicolas Slonimsky, the composer describes what he calls his “periods of development” as follows: from childhood until his departure from Russia – instinctive composing (most characteristic and well-known works are the Bagatelles); 1918-1920 – engrossment in pianism (characteristic works include the first piano concerto and the Arabesques); 1921 – 1930 – polyphony, counterpoint as well as the ‘nine-step scale’ (characteristic works include Inventions; Violin and Cello Sonatas, second quartet, Quintet, Symphony, Sobeide’s Wedding); 1930-33 – increasing use of rhythmic principle, firm and soft intervals, Eurasianism (most characteristic works include Concertino, third piano concerto); 1933-1941 – folklore ‘healing’ influences (typical works include Russian Dances, Trepak, Chinese Etudes, Georgian Suite and the Legend of Razin); 1941 – 1944 – Sturm und Drang – blending of styles, the “search of unoriginal instead of original which was caused by writing so much conventional Gebrauchsmusik”; 1954 up till now – the seeking of pure creation and broad form. In an earlier unpublished archival analysis, Tcherepnin lists his own compositional devices and methods with approximate annual milestones that enable us to chart the development of his processes in more detail: (1) linear polyphony (2) synthetic scales [both from 1920 onwards] (3) sound conception c. 1927 (4) ‘prose’ meter c. 1931 (5) Improvisation c. 1940 (6) patterns – early forties and fifties (7) East and West from c. 1927 onwards.
 Written in 1967 for Slonimsky’s article on Tcherepnin which appeared in Tempo, 87 (1968-1969), 16 entitled ‘Alexander Tcherepnin, Septuagenarian’.
 Tcherepnin characterizes the nine step scale as consisting of “three joined tetra chords: it can be transposed three times (each time by a half tone); the fourth transposition will repeat the exact pitch sounds of the fundamental scale.” [The entire explanation of this approach, including his definition of hard and soft intervals, exists in manuscript. See, PSS 76 (NY)]
 These are identified in his explanation as ‘hard and soft’ intervals. Tcherepnin identifies hard intervals or chords as those that “exclude thirds and sixths”; “harmony in hard intervals is limited to four parts”. On the other hand, harmony in soft intervals is built on thirds.
 PSS W20, Diagram W19.