All that can presently (October 2025) be gleaned about by internet searching is that Henry Dennis Carter is the one-off composer of Halifax Rag (1910) published by C.C. Cocroft Music Co., Thomasville, Georgia, USA. He was the African-American janitor of the said publisher.
Many thanks to anonymous surfer Altolat who provided much of the above by Email in October 2025.
Surfers are welcome to contribute any further information about this composer.