When Brahms was young, he had to play in rowdy taverns to help support his family.

Dance music was what the people in the taverns wanted, and Hannes would sometimes relieve the monotony by improvising variations on the popular waltzes of the day.  But what finally made his work endurable was the discovery that while his fingers were mechanically pounding out familiar tunes on the broken-done piano, he could at the same time read a book.

Source: Goss, Madeleine & Schauffler, Robert (1943) Brahms The Master. New York: Henry Holt and Company, pp.40-41