The music of Mozart is considered art, while that of Slaughter and the Dogs is not. This use of the term art, which distinguishes between different musics, literatures &c, emerged in the seventeenth-century at the same time as the concept of science. Before this, the term artist was used to describe cooks, shoe-makers, students of the liberal arts &c.
When the term art emerged with its modern usage, it was an attempt on the part of the aristocracy to hold up the values of their class as objects of 'irrational reverence'. Thus art was equated with truth, and this truth was the world view of the aristocracy, a world view which would shortly be overthrown by the bourgeois class. As a revolutionary class, the bourgeoisie wished to assimilate the 'life' of the declining aristocracy. However, since the activities of the bourgeoisie served largely to abolish the previous modes of life, when it appropriated the concept of art it simultaneously transformed it. Thus beauty more or less ceased to be equated with truth, and became associated with individual taste. As art developed, 'the insistence on form and knowledge of form' and 'individualism' (basically romanticism) were added to lend 'authority' to the concept as a 'particular, evolving, mental set of the new ruling class'.
Thus, rather than having universal validity, art is a process that occurs within bourgeois society and which leads to an 'irrational reverence for activities which suit bourgeois needs'. This process posits 'the objective superiority of those things singled out as art, and, thereby, the superiority of the form of life which celebrates them, and the social group which is implicated'. This boil down to an assertion that bourgeois society, and the ruling class whitin it, is 'somehow committed to a superior form of knowledge'. From this we can deduce that art will continue to exist as a specialised category until capitalism itself has been abolished.