What libraries and functions is the https://www.vertigomusic.com application using to allow two parties to listen to music at the same time?
The only way music can be played in Vertigo is if a user has first linked a premium streaming account as their legal access point.
The only thing being shared between the listen live host and listeners is the song ID and starting timestamp. Unlike traditional radio where one song is broadcast to multiple people, on Vertigo every single person involved in a listen live experience must have legal access through Apple Music or Spotify Premium to consume the music being played. For example, in a listen live session with a host and three listeners, every song played would log four streams of that particular song: one from the host and one from each of the three listeners.