Can someone resolve this script that involves SoundId and ImageId?

It is not playing the sound because you are...

1. Changing the texture of a decal to a sound id. Don't know what you were thinking, this won't make anything appear.
2. Not changing the SoundId of the sound.

To fix this, make sure you change the SoundId property of the sound and don't change the texture property of the decal unless it's an IMAGE you are changing it to.

Fixed script:

local arrow = game.Workspace.Arrow
local disc = game.Workspace.PlainDisc2.Decal
local sound = Instance.new("Sound", disc)
debounce = false
radioOn = false

function onClicked() -- Clicked
    if not debounce then
        debounce = true

        if not radioOn then
            radioOn = true -- Turn Radio on
            disc.Texture = "rbxassetid://238387775" --Uptown Funk
    sound.SoundId = "rbxassetid://210232032"
            arrow.Rotation = Vector3.new(90, 45.631, -180) -- Turn to turn the music on
            sound:Play() --Play it
        if not radioOn then
            radioOn = true -- Turn Radio on
            disc.Texture = "rbxassetid://98698696" --Gangnam Style
            sound.SoundId = "rbxassetid://163211519" --Play Gangnam Style
            arrow.Rotation = Vector3.new(90, 45.631, -180) -- Turn to turn the music on
            sound:Play() --Play it
        elseif radioOn then
            disc.Texture = "" -- Set Disc texture to nothing
            radioOn = false -- Turn Radio off
            sound:Stop() --Stops the sound
            arrow.Rotation = Vector3.new(-90, -45.631, 0) --This arrow should go back before the disc is plain and radioOn is false
            print("Off\n".."PlainDisc") -- prints
        end

        debounce = false
    end
end

script.Parent.ClickDetector.MouseClick:connect(onClicked)

On second thought, I don't really understand what you are asking. Hopefully I have answered your question, if I didn't tell me what you are still confused about.