Possible Clues:

• Thin wires in light bulbs
• If mantles are replaced, these may replace them
• If they start up they sound sad but light
• If it's the turn of sorrowful sounds they may be light ones
• If they turn sad, make light of them
• If they turn sad, one may make light of them
• They're glowing if they turn up for sorrow
• If it turns and mourns, it makes them light
• If in turn they sound sad, one may make light of them
• Flame isn't put out - they glow in the dark