Music script help?

Where would I put a "Stop" so when I click a text button, the music stops?

local ContentProvider = game:GetService("ContentProvider")

local totalWait = 20 --only wait for 20 seconds max

local queueSize = ContentProvider.RequestQueueSize

function UpdateQueueSize()
	queueSize = ContentProvider.RequestQueueSize
end

function WaitForSoundToLoad()
	local start = tick()
	while (ContentProvider.RequestQueueSize > queueSize) and ((tick() - start) < totalWait ) do
		wait(0.1)
	end
	if (start - tick() > 1) then print("Took " .. tostring(start - tick()) " seconds to load") end
end

function PlaySound(id)
	if id == nil then print("Invalid sound") return end
	local sound = Instance.new("Sound")
	sound.SoundId = "http://www.roblox.com/asset?id=" .. tostring(id)
	UpdateQueueSize()
	sound.Parent = game.Players.LocalPlayer.PlayerGui
	WaitForSoundToLoad()
	sound:Play()
end

local TextBox = script.Parent:WaitForChild("TextBox")
local TextButton = script.Parent:WaitForChild("TextButton")

TextBox.FocusLost:connect(function(enterPressed)
	Game:GetService("ContentProvider"):Preload(TextBox.Text)
end)

TextButton.MouseButton1Click:connect(function()
	PlaySound(tonumber(TextBox.Text))
end)