Play Different Music in Different Areas?

I think the best option is to create a localscript in the StarterGui or PlayerScripts. Check if they are in the lobby by checking their vector and comparing it to the lobby's vector. If they are in the lobby, play lobby music. If they aren't, play map music. Below is an example where the lobby is 6 parts each in a folder

local lobby = workspace.Lobby
repeat wait() until game.Players.LocalPlayer.Character

local function InLobby()
    local plrVector = game.PLayers.LocalPlayer.Character.HumanoidRootPart.Position
    if plrVector.Y > lobby.Ceiling.Position.Y or plrVector.Y < lobby.Floor.Position.Y or plrVector.X > lobby.WallLeft.Position.X or plrVector.X < lobby.WallRight.Position.X or plrVector.Z > lobby.WallFront.Position.Z or plrVector.Z < lobby.WallBack.Position.Z then
        return false
    end
    return true
end

while true do
    wait()
    --Play lobby music
    repeat
        wait()
    until not InLobby()
    --Stop lobby Music
    --Play map music
    repeat
        wait()
    until InLobby()
    --stop map music
end