Musical aesthetics is concerned with the beauty and expressiveness of music, and in particular with properties of this kind as they are perceived by hearing. It designates a field of philosophic thought that arose in the West largely during the course of the 18th century, reached its maturity in the 19th century, and has been considerably enlarged and transformed in the 20th century. Although this is not to say that aesthetic concerns are absent at other times and places, yet the specific historical occurrence of a continuous and systematic area of investigation must obviously be distinguished from a universal but essentially implicit and undeveloped feature of human experience. Aestheticians have the most varied background imaginable; the definition of the field, diffuse as it is, is considerably more precise than the circumscription of its practitioners. As a glance at our List of Authors will reveal, these range from philosophers and scholars to critics and composers, with corresponding differences in the whole complexion of the ideas that are advanced and in their musical or intellectual sophistication.