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Is it the last question "Tell me what tune do I no longer hum?" that I have to answer explicitly?

That's right

Ok here it is.... I have no f*** idea. :D I know that some parts are not working anymore, like the drill. So maybe it's the tune of the drill. :P But what does that have to do with the surroundings of the sun? I give up... curious to see the answer. Nice riddle.... did you came up with it yourself?

No worries, maybe you'll get a flash of inspiration, otherwise you at least paved the way for someone else to solve it. As usual you've already earned a reward by coming this far.