[HS]

Maybe you can achieve a resonance of the free bodies above the platform by moving the platform with a commonly achievable frequency. Because right now its going pendulum->platform->pendulum. But the pendulum->platform force is random and unsteady because of the feedback loop & multiple pendulums. But since all the metronomes have to compromise their ideal frequency anyways, to take advantage of the energy saving common frequency, you can just induce a ball park frequency in the base, and they should all sync to it. It's tricky with soft objects like jelly though, because you get huge delay and dampening at high frequencies, so I don't know how you'd get all of it to synchronize.