If you have Prime Music downloaded to a mobile device, you can play that downloaded music and stream Prime Music from another device at the same time. You can download Prime Music to a maximum of four authorized devices on your Amazon account. read more
A device can only be authorized to one Amazon account at a time. You can deauthorize a device and authorize it to another account once every 180 days. To do this, open Amazon Music for Web or the Amazon Music app, and sign in using the account you want to authorize. Then, try to play or download a title from My Music. read more
If you're already streaming Prime Music on one of your devices and then start streaming Prime Music from another device, you'll see a notification asking whether you'd like to continue streaming from the new device instead. read more