It's the little sibling of the Marble Machine: 84 notes, all piano, about 26 seconds a lap. Place it north-south in the equator region, between rows -80 and 40. Drop 7 items (photons still the shiny choice) in the box at the start, then place a satellite substation on the gate row at the south end to start the song. It loops as long as the substation is there; lift it after the last note and every lane parks at its gate.
The gates need their own power; the print powers everything else.