How do I make it so this sound plays when a person joins?

I am not a good scripter. But I think this is what you need.

game.Players.PlayerAdded:connect(function()
    game.Workspace.WelcomeSound.Sound:Play()
end)

It's a function that plays the sound when a player is added. Hope this helps. I'm sorry if it doesn't. If WelcomeSound is the name of the sound you want to play you just do:

game.Workspace.WelcomeSound:Play()

while true do
wait(1)
script.Music:Play()
end

Then Put Sound form advanced objects. You make make it loop in Properties.