At the time when Sontag wrote this, pop art was very popular, which had room only for experience, but hardly much for interpretation. This was also a fall-out of the fact that art critics just before this time were very eager to categorize every work of art into certain theories and pre-conceived notions, which made way for a very forced manner of looking at things.
It is also true that music needs to be analyzed in order to be learned, and this involves the dissection of their beloved medium for music lovers who also yearn to master it. But after one has absorbed the technicalities of music, they become a sort of second nature, and do not hinder the love and appreciations of the art form. In fact, when one is aware of how exactly the music is made, the enjoyment becomes keener. It is just a matter of going through the difficult transitional learning phase without losing interest or ardor.
From our discussion here it is clear that analysis and interpretation are necessary in order to appreciate and gain an understanding of art. But it is important to do this while keeping fresh the immediate experience that art provides, so as to fully enjoy it and not impose any meanings that even the artist may not have intended in the first place.