the first thing you have to do is make Android apps as good as possible to interest people download songs using your Android app
after the application you can visit some advertising companies for Android among which it admob it is most famous for under the Google Adsense
Put and adjust the ads with your android apps do not get too annoying users so users will uninstall your application
after that all finished uploading your application on the websites of the most famous Android app's Play Store