Many modern cars have Bluetooth streaming (also known as A2DP), which is different from hands-free calling. This option works well with Muse because you can enjoy audio from the car stereo system without wires. If your car supports Bluetooth remote control (AVRCP), you will be able to skip tracks and see visual feedback on the in-car screen (head unit).
Here's a video guide for setting up Bluetooth on iPhone:
And here's the guide for Bluetooth on Android:
How to check if your car supports Bluetooth Streaming
If you can pair your phone to your car and play music through the car stereo system, you have A2DP. If you see the currently playing song on the car screen (head-unit) or skip tracks using steering wheel or dashboard controls, then you also have AVRCP.
Using Car Bluetooth
Select the iPhone/Android system settings app and choose Bluetooth. Make sure you are connected to the car stereo Bluetooth - it may be the name of your car manufacturer, MyCar, UConnect, etc. Also, make sure you are not connected Muse as the Bluetooth audio device.
On iOS, if you see "Muse" and an (i) next to it then select it to disconnect. That option is for Aux playback.
Once you've confirmed car Bluetooth is paired, return the Muse app and selected Bluetooth from the "How do you play music in your car ..." screen. Follow the instructions in the app to test and complete the setup. Remember to choose Bluetooth as your audio source in the car stereo system.
For help choosing the right audio output, see the Audio Output Guide.