Sergey Prokofiev

Sergey Prokofiev

We spent hours at the piano. I often improvised for him with a view to encouraging him to do the same. I have always attached much importance to the art of improvisation at the piano, I believe this to be most valuable in developing the creative imagination of the future composer. And, sure enough, I would no sooner rise from the piano than Seryozha (Prokofiev) would sit down and begin improvising.

Sergei Prokofiev: Autobiography, Articles, Reminiscences
Reinhold Moritsevich?