Amazon is making its Echo speaker a little more convenient to use for the millions of Spotify and Pandora listeners out there. You can already play music from streaming music services by speaking commands like "Play ______ on Spotify." If you forget to add the "on [service name]" at the end, though, Amazon will try to play content from Prime Music. But now Echo owners can change the default music source so that the device will always play tracks from Spotify or Pandora; you don't have to specify the app's name anymore. This works on the Echo, and should also be supported on the Echo Tap and Echo Dot devices. Spotify can be chosen as your preference for on-demand listening, and Pandora can be made Alexa's go-to music station service.
To change where Echo plays music from by default, just open up either the Echo companion app or the web-based preferences site. There, you'll see a new option listed as "Customize my music service preferences." Click or tap that and you can tell Alexa that you'd prefer to get your music from a service that's not Prime Music. It's definitely something you should do if you're a Spotify subscriber. Prime Music's catalog is way more spotty than proper subscription music services, so you might get stuck with a live version or just fail to find whatever you're looking for. It definitely makes Alexa / Echo feel a little more open and customizable, which is a very good thing.