The song of Blackish Nightjar is short and not loud. It variously is described as "a soft, purring pu'r'r'r'r't or qu'r'r'r'rt repeated 3-5 times in about 4 sec. or more" (Hilty and Brown 1986); as "a soft pr-r-r-r-t repeated several times in succession, often followed by [a] long pause before another series is given" (Ridgely and Greenfield 2001b); and as a "quiet purred series of wurt notes" (Lane, in Schulenberg et al. 2010).
For a representative audio recording with sonogram, see audio
Other vocalizations of Blackish Nightjar include a cluck or ptink alarm call, as when flushed from the nest by humans (Cleere and Ingels 2002, Jackson and Ingels, 2010), and a guttural hissing during threat, defense, and distraction displays (Cleere 1998). The alarm call of nestlings is a small peep (Cleere and Ingels 2002).