We call them people who like listening to music. There is no special name for them.

Groupies - Fans - music junkie some bands name their fans: Greatfull Dead fans = deadheads Steely dan fans are part of the Dandom (these are the only ones I can remember, but several bands do this.)

Just a fan. Also in some circles here in North America when I was growing up (emo, punk, indie rock, etc) you could be called a "scenester" if you were just an obsessive fan who never actually did anything of their own :) It's kind of an insult along the lines of "hipster"..

Just a music lover

We don't use the term "music geek". We would say they appreciate music or at least enjoy listening to music. There is no special term for them whether they play an instrument or not. If someone does play an instrument well, we would call them a musician. But a lot of people like to listen to music.