The commenter implies your coil whine comes from "dirty power" from your power strip (not a perfect sine wave). This may or may not be the case, so it's at least one thing you can try out.
Great details! I know the difference personally, but this is a really nice explanation for other readers.
About the last point though: I'm not sure Go always uses the maximum amount of kernel threads it is allowed to use. I read it spawns one on blocking syscalls, but I can't confirm that. I could imagine it would make sense for it to spawn them lazily and then keep around to lessen the overhead of creating it in case it's needed later again, but that is speculation.
No, Patrick, soup is not an instrument.