The Days of Exchanging Letters with Tchaikovsky

====Consumption Instructions==== 0. Piano × cello; sponsored composer × fanboy businessman 1. This is a beautiful article! Tanmei! Tanmei! 2. It is currently confidential and there is no information that can be disclosed. ================ [The idea of writing about Tchaikovsky came from his brilliant piano concerto, but the real impulse to write the article came from an interesting comment made under a certain cello piece - "In my eyes, piano and violin are BG, while piano and cello are BL." The musician part of Encountering him in history starts with "piano and violin" and ends with "piano and cello". It just so happens that Tchaikovsky in history was also such a musician.