In the Start Menu search box type Settings. In the settings search box type Default Apps.
Find the app that you want to use and select it. Scroll down to mp3 and click the icon at the right. Click Set Default.
OR
Right-click on the desired file > Open With. Choose the app you want to be the default from the list or scroll down and Choose Another App.
Explorer (the file manager) opens. Locate the app you want to open mp3s and double-click it. Click Always, if available.