What does this mean? Music literature? How is this philosophical? ?

It's saying that music isn't *less* concrete than words, it's *more* concrete, more solid and real. More precise. Words mean different things to different people, but music carries a certain essence, a certain real experience, that bridges that divide. Music contains emotion more clearly and unchangeably than words. This is philosophical in that it expresses an opinion about music, words, and emotions--about how thoughts and emotions are created and expressed.