It turns out that hobby drones are good for more than just buzzing around tech shows and generally creeping us out. They can also play a pretty cool version of “Thus Spake Zarathustra.” A startup called KMel Robotics this week dropped a YouTube video of its programmed drones playing the Richard Strauss composition famously featured in 2001: A Space Odyssey, as well as “Carol of the Bells” and “The Star-Spangled Banner.”