One way to expand it could be to add some other objects. Maybe a sun that pulses to create a base beat. A clump of asteroids that cover an entire octave, but lack the momentum to escape the planet they bounce off from, so they create a melodic repeating note pattern when repeatedly bouncing off a surface. A black hole that spits out the planets out the white hole placed elsewhere, to create dynamic "loops" of orbits/bounces. All kinds of strange generative things could be done.