You'd still need the Spotify desktop client open (Winamp2-js would function as a remote), but you could do things like populating the playlist window with a user playlist.
Unfortunately, you can never fully work. DRM means we can’t get raw access to the audio stream so EQ, visualization, balance, (for example) won’t work.
Pretty sure you can get it for visualization...
If you have an example, send it my way! I believe the Analyser node cannot get output from a tainted source.
You can use a virtual audio cable. Spotify -> virtual cable -> winamp -> real audio out
Can you recommend a "virtual cable" javascript library that is compatible with DRM output? I can't seem to find anything.