Opus, the Latin word that we apply to musical compositions, has the twin meanings of work and riches. We hear it in operate and opulence. Good work enriches the world and also enriches the worker; it draws on our creativity, our ability to imagine actions before carrying them out, and our freedom to act on those images, guided by intelligence and skill. The medieval guilds of carpenters, weavers, dyers, and millers spoke of their trades as mysteries.

Scott Russell Sanders, Writing from the Center