The reality is that it is a next word prediction machine. There probably aren’t any examples in the training data where people are writing music reviews on something that isn’t music. It probably interprets the sound as best as it can as “music” (and the best it can do this is likely very bad in the first place), and then, since the prompt was about reviewing music, it uses next word prediction to write a music review, which of course turns out looking like a typical music review. It’s not really interpreting the sound as “not music” especially since you told it it IS music.