There is some kind of interplanetary conflict going on between different human factions (aliens may or may not be involved). As a relatively minor plot point a group of or all humans have lost the ability to appreciate or comprehend music through a virus or other disease. I believe it changed their DNA so the (loss) trait was inherited.
That's Alastair Reynolds "Century Rain" (my personal favourite among Reynolds' novels). The war is between two human factions - "Threshers" (derived from "threshold", since they don't allow technology beyond a certain level of complexity) and "Slashers", who embrace nanotechnology. Earth was an early casualty in their conflict.
No aliens per se, but Alien artifacts (artifical wormholes, copies of planet Earth).
Made it even into TV tropes (there goes the rest of your day):
Dreadful Musician: Averted in Century Rain: in an early scene the protagonist is walking into a superior's office while he plays a violin, with her Internal Monologue noting how grating and painful the music is. It is then revealed that she, along with a large portion of the rest of the human race, were infected with a designer-disease called 'amusica', which prevented people from enjoying music, to ruin their side's morale. After all, someone who can't appreciate music can't get patriotic fervor from their anthems, now can they?