ESTUDIO (1)

Although Robert Schumann did not busy himself with piano teaching, he wrote much about music and musicians.  He thought that exercises, scales and etudes could be useful, but that to practice mechanical exercises for many hours would be as absurd as trying to pronounce A, B, C faster and faster every day.  He considered better to study a complex musical composition comprising all possible kinds of difficulties and offering good material for technical work. 

The Art of Piano Playing.  A Scientific Approach (página 6)

George Kochevitsky.