The display vocalization of Capuchinbird is described as a "moo" call (Snow 1982) or as a loud "grrrrraaaaaaaaaaaooooooooooooooo" (Hilty 2003), reminiscent of a distant chain saw, and often is preceded by a hissing sound that only is heard only at close range. For a representative audio recording with sonogram, see audio
Singing appears to be cooperative as nearby birds tend to avoid overlapping with the display songs of others when at a lek (Snow 1982).
Males may utter a short, frog-like croak, "rounhh" between songs, especially at midday (D. Ascanio, in Restall et al. 2006).
Females and immature males give a "half-moo", with the female version being extremely raspy and harsh (Snow 1982). It is called the "half-moo" because while being nearly as loud as the call of the male, it only lasts about half as long.
While foraging also has "a growling wark" (Kirwan and Green 2011), and a "kack" when alarmed (Snow 1982).