Have at least two constant notes throughout your scene.
Anytime.
It sounds like a negative word. A bad phrase. To drone on. Something that you want to get away from. A person you don't want to listen to. That really awful PowerPoint presentation given by that one consultant brought in for long meetings to talk about buzzwords with lots of one-note buzzing. An endless repetition.
In music, however, a drone is a useful concept employed not only in compositional works, but even in individual instruments. There are a wide variety of reasons one might use a drone. The drone can be employed to ground the work throughout the piece as a drone is an ever-present note throughout. The clearest example of a drone is the bagpipe. While notes can certainly be played, there are other notes that constantly "drone" without needing to be consciously played. Those notes just are. The instrument itself drones, and that makes it recognizable.
One of the constant calls in so-called traditional playwriting is that characters must change. This is often referred to as a character arch (though there are other terms). Often this idea of change is embedded into the very core of what it means to write a play. This exercise forces you to have at least two constant notes.
There are many ways to think about this. Here are some that I've employed.
Now that you've droned your way to a play do you feel changed or unchanged. Are your characters changed for the better or for the worse? Is the structural change for good or for ill? Will you drone again?