“On and On,” the new Missy Elliott song from her forthcoming album Cookbook, is really amazing: gurgling synthesizer lines over a heavy booming beat, and the art of declamation honed sharp as a razor. Wow. Produced, not by Timbaland, but by the Neptunes, and one of their best tracks ever (enough to make you forget “Milkshake”or “Drop It Like It’s Hot”).