Trumpeters are very vocal and produce a wide variety of calls. The call for which they are named is quite loud (though not very trumpet-like), and consists of 3-5 notes introducing a resounding Oh-oh-oh-oh-ooooooooh! and seems to be used by all adult birds to assert territoriality.
Terrestrial predators elicit loud squawks, while snakes cause members of a group to produce a short, medium-pitched rapid hm-hm-hm-hm-hm call.
More work on vocalizations has been done on the related Pale-winged Trumpeter (Psophia leucoptera), but as these species are closely related, the Gray-winged Trumpeter's vocalizations likely are very similar. Sherman (1996) describes the following calls among Pale-winged Trumpeters:
-Birds also make a harsh antagonistic threat call that consists of a number of staccato cackling notes, often ascending.
-A high pitched twittering, which is often given by young chicks, is produced by subordinate birds while interacting with more dominant flock members.
-Chicks also produce a whistle-like, two noted begging call, with the second note higher than the first. This call is also given by adult birds while begging for food.
-Birds that are carrying food in their beak with the intention of feeding another bird will give a nasal enhh-enhh-enhh-enhh call.
-Aerial predators (hawks) elicit a low pitched call that is somewhere between a hum and a growl.