I know this thread will start debate -- but hear me out.
I've never once thought that Michael performed some of the Jackson 5 songs live at the 30th Anniversary show. Some songs (Can You Feel It, I Want You Back) don't seem like they have live vocals, while others (Dancing Machine, Shake Your Body) do. It's known that Michael re-recorded some of the Motown hits back in '89 for the cancelled Decade compilation, which fuels my belief that he may have been lip-synching. For instance:
@ 0:52 -- Michael looks like he begins to lip-sync the first verse, not knowing that the vocals weren't there yet.
@ 1:36 -- I highly doubt that Michael would have kept smooth, crisp vocals right during and after a spin. He never has before.
@ 1:38 -- Michael moves the microphone from his mouth a little early, and perfect vocals are still heard.
Also, if you will, compare the above performance to this one:
The vocals on Dancing Machine are obviously live -- Michael mumbling a few syllables, singing certain lyrics faster so he can catch his breath, not to mention a slightly nasal sound, as if he had a stuffy nose. Also, the vocals have a "live" element to them that I can't really explain clearly; they SOUND live, whereas the I Want You Back vocals sound
Now, I would fully believe that Michael was singing every song live if this concert had taken place back in '81 during the Triumph Tour (at times on the live CD, the vocals are perfect and clear, as if Michael was lip-synching). But this performance was by a 43 year old man, whereas those were by a 23 year old man.
This is just what I have seen. I may be wrong, I may be right. Either way, opinions?