Ever heard of a theremin? Created by a Russian inventor who gave his name to the device, it’s a non-contact electronic musical instrument — you play it by waving your arms at it. Although it sounds comical, its otherworldly tones made it a staple of movie soundtracks, and now you can try it on your iPhone. No, it doesn’t work quite the same way, but by waving your iPhone in just the right way, you can generate quite a pbumable imitation of what’s perhaps the weirdest of all instruments.