It won't be exactly sync'd for all users. You can play a piece of music, which may be off by approximately each player's latency. Event Sounds can do it based on any MonoBehaviour event. Check the "Multiplayer Broadcast" checkbox.
I am trying to have a piece of music start in the Main client and then when every additional player joins the music is synced. however, when players are entering atm the music doesn't trigger for them.
Should I use a playlist or something for this. At the moment I', just using a Sound Group and an Event Sounds component set to to OnStart.