Answer: Dann Huff: Guitar. Greg Phillinganes: Keyboards. Glen Ballard, Randy Kerber: Synthesizers. Background vocals: Siedah Garrett.
Explanation: There is definitely some poetry to the fact that "Man in the Mirror," recorded at the peak of Jackson's career, is a song about an individual struggling to reconcile himself to society, self-image, and personal responsibility. (Although, notably, the words were written by a woman.)