monotone -- (a single tone repeated with different words or different rhythms (especially in rendering liturgical texts))
Overview of adj monotone
The adj monotone has 2 senses
monotonic, monotone -- (of a sequence or function; consistently increasing and never decreasing or consistently decreasing and never increasing in value)
flat, monotone, monotonic, monotonous -- (sounded or spoken in a tone unvarying in pitch; "the owl's faint monotonous hooting")