The song of Scaled Antpitta is a rapid series of quavering, hollow notes lasting 2-7 seconds, slowly increasing in volume and pitch and then quickly becoming quieter at the end: cau, cau, cau-cau-caucaucaucau, cau. Krabbe & Schulenberg (2003) provide a detailed description of the song of regulus, stating that songs generally include 30-50 notes delivered so quickly (i.e. 14-17 per second) that it generally sounds like fewer. Delivery pace, after a few introductory notes, is rapid in the beginning, slowing towards the end.
For a representative audio recording with sonogram, see audio
Krabbe and Schulenberg (2003) note that the songs recorded in southern Peru (sororia) differ in having the first portion delivered at a much slower pace (only 6 notes per second), with the entire song slightly longer and being composed of only 18-23 notes; similarly, Lane (in Schulenberg et al. 2010) describes the song of sororia as "a slower-paced (6 notes/sec maximum) series of hooted notes that accelerates-decelerates at the loudest and highest-pitched notes, then accelerates again slightly: poo-poo-pu-pu'pu'pu-pu-POO-POO-POO-pu'pu".
Braun et al. (2003) describe three vocalizations of roraimae. The most frequently heard song was described as a long series of low hooting notes with three longer, more emphatic notes in the middle. They also occasionally heard a higher-pitched and somewhat screech-owl-like song. The third song, given most frequently at dawn, was a shorter-simpler version of the owl-like call described above.
Stiles and Skutch (1989) describe a low, pig-like grunt or croak given in alarm in Costa Rica.