Mopidy is described as 'music server which can play music from Spotify , or from your local hard drive. You can use your favorite MPD client to search for music and manage the playlist' and is an app in the Audio & Music category. There are more than 10 alternatives to Mopidy for a variety of platforms, including Linux, Windows, Self-Hosted solutions, Mac and Online / Web-based. The best alternative is Funkwhale, which is both free and Open Source. Other great apps like Mopidy are Ampache (Free, Open Source), Exaile (Free, Open Source), Subsonic (Freemium) and Koel (Free, Open Source).
Music Player Daemon (MPD) is a flexible, powerful, server-side application for playing music. Through plugins and libraries it can play a variety of sound files while being controlled by its network protocol.
Airsonic is a Free and Open Source community driven media server which allows you to stream, transcode, manage, and share your personal audio from anywhere via an HTML web browser or any number of apps (available for both iOS & Android).