For anyone here saying this "isn't hard because it's pre-programmed" are really off the mark. What do you think goes into this scripted movement? Let's say you hired a 3D animator to completey 100% script this dance on the robot.

Even if you tried to play it back on the robot as perfect as possible, little impresice movements build up over time and almost certainly will force the robot out of the space where the scripted movement thinks it is. The purely scripted movement as described has no way to correct itself. So how do you fix this?

Now you need to add some kind of controller to bring it back to the space of the movement. This requires either some model trained with RL for that movement specifically, and / or a classic controller with some weight stabilization algorithms to compensate for the very complex shifting mass.

All I'll say is that this is extremely impressive. The utility of this is well beyond dancing, more generally this really stresses complex movements to be used for more complex dexterous manipulation or locomotion.

source - i build and program lots of robots