Here is a superb critical assessment by Bob Grant on Scruton’s work (H/T to BG).
Roger Scruton’s 530-page blockbuster The Aesthetics of Music was published by Oxford University Press in 1997. A paperback edition followed two years later. Neither received more than a handful of notices, a few appreciative, but some grudging and some actually hostile. As its quality has come to be recognized, and as the resentments it provoked have either died down or found newer targets, the book has gradually achieved a certain canonical, even classic, status. Students of the subject now seem to feel that, however unpalatable some of its conclusions may have been, it can no longer safely be ignored. The questions, it appears, are the right ones, even if we don’t care for Scruton’s answers. (Thus far the pop critic Simon Frith, who said as much from the start.) The book actually covers more than aesthetics, being nothing less than a complete philosophy of music. There are some major omissions: of non-Western music, for example. But they are justifiable, given that Scruton’s project is analytical rather than documentary. Some extra-aesthetic matter is inevitable, since it is scarcely possible to deal in isolation with any art form’s purely aesthetic element (assuming there really could be such a thing). But with music Scruton casts his net wider even than he did in his early The Aesthetics of Architecture (1979). In The Aesthetics of Music he extends his inquiry to virtually every aspect and ramification of the phenomenon in question.