Jelly -Your best bet is to make an iTunes or Spotify/Pandora playlist to play on the background of your personal computer if you want music during the ceremony. Thankfully, there's no option to play music in Hangouts that I know of. (Personally, my volume would be firmly shut off in such an event - I get enough noise and music during the hours my kids are awake. I love them with my whole heart, but man, my ears are TIRED once they're in bed.)