A recent issue of NORTH AND SOUTH magazine has a good summary of the debate about black Confederates. The evidence is somewhat ambiguous, but there's NO doubt that some blacks fought, and a LOT of blacks served with the Confederate armies. Voluntarily? Probably mostly not, but then thousands of white southerners served only after being conscripted. It is certainly true that hundreds of blacks got Confederate pensions from Tennessee alone.
I'll post the story of my Uncle JJ and his body servant Levi Miller; it deserves to be told.