Amazon Music made a surprise appearance in the Microsoft Store today, as spotted by Windows Central. Unfortunately, it's not available to download yet in all regions, but you can easily find it on the Store by searching for it.
The app is currently PC-only, which means that you won't be playing your Amazon music on your Xbox anytime soon. It also means that this is a Centennial app, a Win32 app that has been converted to an APPX package so it can be downloaded from the Store.
You can use Amazon Music to listen to any of your music from the company, whether you subscribe to the premium Music Unlimited service, the more basic Prime Music, or if you've just purchased content from the firm's MP3 store.
Frankly, this is great news for Microsoft. After the death of the company's in-house Groove Music Pass services, the ability to offer third-party services was critical. Spotify was already in the Store, and we know that iTunes is coming, even though it's delayed. The addition of Amazon Music makes the Store selection even more well-rounded.
You can find Amazon Music on the Microsoft Store here, and it should be available for download where you are fairly soon.