Is goyish music really assur? What’s the difference between listening to non Jewish music and eating non Jewish bread with a kosher symbol?
Although I’m not really clear about your comparison with bread, there is no problem in principle with non-Jewish music.
Yet, this will depend greatly on the nature of the music. There is for instance a gulf between classical music (which is also non-Jewish) and most modern pop-music, where both the lyrics and even the accompanying music often involve improper matters.
Therefore, although there is no blanket prohibition, one should use one’s discretion in deciding which music to listen to.
See Maaseh Rokeach Tefillah 8:11 who writes that non-Jewish music can involve a prohibition of be-chukoseihem.
However, this will apply specifically if a person is seeking to adopt non-Jewish culture, and not for somebody who is listening to music for his enjoyment or to wind down after a day’s work, and so on.
Note that much of what is today “Jewish music” originated from non-Jewish music (it is not by chance that Sefardic “Jewish music” is so different to Ashkenazi “Jewish music”), so that clearly there is no blanket prohibition. Moreover, modern Jewish music is to some degree non-Jewish music “in disguise.” Yet, the different lyrics and the different “atmosphere” are of course significant.