Is it possible to run music in the background?

Yes, there are several options:

• You can stream music through the Main Stage and the mini player, then everyone in the event can have it on and listen to the mini player, for this you can simply use a YouTube video for example.
• You can also embed a Spotify playlist in a room, but only the people who actually have a Spotify account can listen actively.
• The most beautiful but also technically demanding option would be to create a user name "Music" via a streaming tool such as OBS and VB-Audio and put it into a room, then you can simply stream the music into the room via the Virtual Audio Cable, but this requires a good internet connection.