Playing music over Bluetooth in Android car unit that only accepts Bluetooth phone call

I have Android car unit on Peugeot 307 SW (2007). It has Bluetooth, but it's only for making calls. I want to play music on it, and I don't want to buy any adapters. Google Maps can tell the directions over the car's Bluetooth as Bluetooth phone call, so it should be possible for other apps to do so.  Is there a way to play music over Bluetooth as Bluetooth phone call? Alternatively, are there music apps that can play music as Bluetooth phone call?