Treatments of music have long been a part of aesthetics: perhaps precisely because music is as abstract as it is--that is, it is not representational, or at least not obviously so--consideration of music raises questions about meaning, and human responses that are very different from those raised by representational arts such as painting or film. While there has been much written on the philosophy of music, I think that a very good place to start is with the work of the philosopher Peter Kivy, who has written on a wide range of topics in the aesthetics of music over the years.
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Does philosophy concerning music have any worth or substance? Or is music simply too abstract for there to be any meaningful philosophical insights gleaned from it?