No, not tiny aircraft, though … those might make a nice accompantiment too.
“Of all harmonic devices, it [a drone] is not only the simplest, but probably also the most fertile,” says musicologist Peter van der Merwe. I don’t know much about him, but the sentiment goes right along with this clip. Here I’m making it up on the fly against the backdrop of a single C# note. Chord progressions can spark ideas for improvisation: Not only does a series of chords indicate a key, it gives you something to react to. With a drone, it’s all on you.