Labor is work that leaves no trace behind it when it is finished, or if it does, as in the case of the tilled field, this product of human activity requires still more labor, incessant, tireless labor, to maintain its identity as a "work" of man. ↗
When a pianist sits down and does a virtuoso performance he is in a technical sense transmitting more information to a machine than any other human activity involving machinery allows. ↗