Found on prince.org. A person stating that there is footage of Michael singing "Keep Your Head Up".
"There is evidence of MJ singing "Keep Your Head Up" in the Cascio's basement LIVE, but there saving it for the video.
The footage shows MJ pausing and stopping and doing multiple takes. There were points where his falsetto was off and he wanted to do it over again. There joking about how it sounds great and MJ is like...We can do better than this.
Judging by the footage, its MJ on about 80% and the rest James Porte filling it out."
Link to the discussion on prince.org: