Yes, I am writing on a book on Duke Ellington, covering the years 1930 - 1943 when he performed at the Carnegie Hall. The Ellington orchestra stayed at the Cotton Club untill 1933 when they went to Europe. Lunceford had a brief stay at CC around 1934 as you mentioned, Calloway stayed a bit longer. Ellington helped Callowy in the early days and received a 10% cut in return.
What was your mothers name? How long did she work there?