New Coder, Help Debugging a Surface GUI That Plays Music?

Hi! I'm just now dabbling in ROBLOX programming (with no prior coding knowledge) so my code will be very crude, so bear with me.

I'm creating a surface GUI that has a large image button in the middle, and two image buttons on either side to cycle the middle image. I don't know the best way to do this, so so far I have a script in the left and right buttons that increases or decreases a _G variable by one every time you click. It looks like this:

script.Parent.MouseButton1Click:connect(function()

_G.song = _G.song + 1

end)

Then I have another script in the big central image button that is supposed to detect if the _G variable equals either 1 or 2, and plays a different song on click depending on the value of the variable. The code looks like this:

mus1=workspace.juke.buttons.music1
mus2=workspace.juke.buttons.music2

while true do

if _G.song == 1 then
	script.Parent.MouseButton1Click:connect(function(one)
	mus1:Play()
	end)
elseif _G.song == 2 then
	script.Parent.MouseButton1Click:connect(function(two)
	mus2:Play()
	end)
end
wait(.25)
end

When I click the big central button however, it plays both songs, not one or the other. Why is it playing both?