I know sims 3 had speakers you could put in your house and you could hear the music from one radio in your whole house. This kind of caused a small problem if you placed these things in a bed room. ...
I found this today. It's a $1 speaker. Put one in every room you want to have music. They sync up. It's for Alternative only as far as I know, but if you put your custom music in the Alternative folder, then it will play it. I installed it today and love it. http://modthesims.info/d/599423
EDIT: They have one for Pop too. Same link. I don't use the Pop station so I didn't get it.
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