Hello and welcome. You cannot separate the background music out of TV shows.
If the broadcast is in Dolby 5.1 and you have a 5.1 set up, you could turn every speaker off but your center speaker but that isn't very practical since there is more than just background music that is carried on the other speakers.
You can't do it. Sorry.
No you are confusing it with the compression system that modern TVs use to lessen the volume of commercials which are often recorded at a higher level than TV shows.
These systems reduce the sound of commercials.
You can't remove the background music from TV shows.