Vocalizations of adults: Azure-rumped Tanagers are rather noisy, which is often the first cue of detection in the field. Birds in pairs or flocks perched or feeding in the forest canopy give various drawn-out sibilant calls, described as se-e-eet or se-a-weet (Hilty and Simon 1977), wi sseeu or ssi wsst (Howell and Webb 1995). A FSEEeee-ew-weEEE? vocalization was interpreted as song by Cooper (2003). Sibilant drawn-out calls range in frequency 5–15 kHz (Eisermann et al. 2011c). At Atitlán volcano, Guatemala, three different sibilant vocalizations were observed (Eisermann et al. 2011c): (1) "a combination of three notes, the first note downslurred, the second upslurred and third note downslurred again" (Sonogram 1a), "a variation of this call is shorter and lacks the final downslurred note" (Sonogram 1b), and a "third vocalization type was an up- and downslurred call followed by a sharp note, siiuu-t" (Sonogram 1c).
Short calls were described as ssi or ssit and "excited twittering" (Howell and Webb 1995), "rapid, clicking t-t-t-t-t" or "sputtering p-p-p-pt-pt" (Cooper 2003). The sharp notes run sometimes into a twitter given during short flights (Sonogram 2a) or into a sharp trill (Sonogram 2b), similar to calls of Common Bush-Tanager (Chlorospingus ophthalmicus) and Emerald-chinned Hummingbird (Abeillia abeillei).
During aggressive behavior towards intruders in the nest area or between adults in a fruit tree, Azure-rumped Tanagers gave a scratchy rrrb-rrrb-rrrb with a frequency range 1.5-11.0 kHz (see sonogram in Eisermann et al. 2011c).
Vocalizations of young birds: "Older nestlings gave a series of zee notes at 9–13 kHz, used as a begging call prior to being fed. The interval between calls became shorter with increased excitement" (Eisermann et al. 2011c) (Sonogram 3).
Two different vocalizations at 7-11 kHz of fledged juveniles were reported. One type was a downslurred sibilant siu note uttured at irregular intervals. This note was sometimes followed by three shorter notes, which can be rendered siu—zee-zee-zee (Sonogram 4a). A second type of vocalization was a double note like zziu-zee (Sonogram 4b).