for a node.js based Google Play Music clone (with android sync application included) + youtube downloading built in (with playlists) + soundcloud downloading built in (with playlists) see my project Node Music Player: https://github.com/benkaiser/node-music-player

I've been working on it for the last few years with a few pull requests from awesome members of the community and I'm about to launch auto-generated mixes that allow you to explore music in a way similar to Google Play Music and Spotify (using lastfm api and youtube: here's the module for it https://www.npmjs.com/package/similar-songs )