Way to listen to computer audio or adding some music playlist

What I do now is changing the mic source to computer audio in windows so I can't show how it visualize music.
It would be cool if one could do that, without changing the system options.
Or maybe some free music playlist could be added or even spotify login.

No files, tests, or entry points are mentioned. Start by locating how the visualizer receives microphone input on Windows and determine whether computer audio can be captured without changing system options. Compare that scope with adding a free playlist or Spotify login; done requires a decided, testable feature rather than several alternatives.

Written by the indexing model from the issue text.