Only male Thick-billed Vireos sing. The definitive sound has been described as a "non-musical buzzy, burry syllable" which is present in most songs (Walker 1998). Their songs have a general pattern of a bubbly chik-didle-wer-chip (Raffaele et al 2003).
Walker (1998) has conducted the only detailed analysis of song variation. In eight populations, she identified eighty different syllables, with thirty-two found in only one population. Frequencies ranged from 720 - 13,760 Hz. Abaco and Andros had the highest percentage of syllables shared, and tended to cluster with New Providence; San Salvador clustered with Turks and Caicos; the Paredon Grande Cay population was separate; Cayman Brac and Grand Cayman clustered together; and Providencia (V. c. approximans) was an outgroup (they do not sing). Songs ranged from 0.46 - 2.77 seconds in length, with 3 - 14 syllables per song (5 - 8 being typical). Northern Bahamas populations had the most song types. Song types tended not to be shared among populations. Individual males sang up to nine song types.
Long song, subsong, or rambling song - syllables with no set pattern - can last over 8 seconds (Walker 1998). The function of this song is not known.