You can turn off radio by going into an airplane mode, then enabling Wi-fi. At least that's how I use my Galaxy Nexus as a media player after I got my Nexus 5.

You can turn off radio by going into an airplane mode, then enabling Wi-fi. At least that's how I use my Galaxy Nexus as a media player after I got my Nexus 5. (and same method works for Nexus 5, so I'm assuming it'd also work on Moto G...)