This list includes 25 black musicians plus 11 cooks and nurses. Nurses include four women. Note that most were on record for brief periods of time (a few months or days).
Earlier in the war most Confederate companies employed two or more cooks, many of them slaves belonging to company members.
On that basis about 4,000 cooks might have been employed in the Army of Northern Virginia during 1862. Most had to go home when the army drastically reduced rations in 1864. The pitiful amount actually issued left nothing to feed servants.
The list also includes nine white Confederates. Some served as overseers, a common occupation where slave labor was present. During the war hundeds, perhaps thousands of soldiers were detailed as overseers. At the end of the war (March-April 1865) hundreds of officers applied for permission to recruit Negro military commands.
Not sure why white Confederates are included among black nurses, cooks and musicians.