I can't get my auxiliary cord music to play from my phone to the stereo I must have turned a button off on it how do I get it

[vaehbug2013]

How do I get my cell phone to play music onto the stereo it did at one time but I must have hit a button and now it only plays through my phone even when it's plugged into the auxiliary cord

 

[Alabalcho]

What happens if you plug ordinary headphones into your phone?