Art is a diverse range of human activities in creating visual, auditory or performing artifacts (artworks), expressing the author's imaginative or technical skill, intended to be appreciated for their beauty or emotional power. In their most general form these activities include the production of works of art, the criticism of art, the study of the history of art, and the aesthetic dissemination of art.
Usually the work of several generations is needed to develop that formal system which later is called the style of the art, from its simple beginning to the wealth of elaborate forms... The interest of the artist is concentrated on this crystallization, where the material... takes, through his action, the various forms that are initiated by the first formal concepts of this style. After completion the interest must fade again, because... "interest" means... to be with... to take part in a process of life... [H]ow far the formal rules of style represent that reality of life which is meant by the art cannot be decided from the formal rules.
Werner Heisenberg, Physics and Philosophy: The Revolution in Modern Science (1958)
In the largest sense, every work of art is protest. … A lullaby is a propaganda song and any three-year-old knows it. … A hymn is a controversial song — sing one in the wrong church: you'll find out. ...
Pete Seeger, Pop Chronicles: Show 33 - Revolt of the Fat Angel: American musicians respond to the British invaders. Part 1, interview recorded 2.14.1968.