If you don’t have a server to run Subsonic (or Nextcloud, or other servers supporting the same APIs), or you prefer a simpler solution, you might wish to try Astiga. In their own words:
Astiga is a streaming service for your own music library. You can play your music wherever you are in the world. You store your music in a cloud storage service of your choice (Dropbox, Google Drive, OneDrive, Backblaze, S3, pCloud and most services that support WebDAV, FTP or SFTP) and Astiga plays it from there. There’s a Web based player, plus an app for Android, and as you know because we implement the Subsonic protocol any Subsonic client should work.
Because you have control over your music, you get to say how it’s organized, what music is in it, etc. We also feel privacy is important.
This version improves the startup time and fixes a problem that prevented it from working with servers that don’t support token authentication (which is a more secure way of passing credentials to the servers, quite important if you’re not using https), such as the Music app for NextCloud/OwnCloud.