https://www.techradar.com/news/alexa-cast-lets-you-control-speakers-through-your-smartphone

Amazon is finding ever more ways to expand Alexa’s functionality. This time, it's giving the Amazon Music app a welcome update with the new Alexa Cast feature.

As of July 26, anyone with an Amazon Echo or similarly Alexa-enabled device will be able to control music playback through the Amazon Music smartphone app, on either iOS or Android.