Crowned Slaty Flycatcher is generally fairly quiet. The song is thin, described as "thin buzzy and rising be-bee-beee-beeez, low whistling pree-ee-ee-er, and a series of squeaky notes, or a two part tsi-tsitsewt-tsi-tsébidit" phrase" (Mobley 2004).
For a representative audio recording with sonogram, see audio
Other vocalizations heard during the breeding season include a "rather weak pseek or high thin pseeet, sometimes repeated in a series (Mobley 2004).
Crowned Slaty Flycatcher also is very quiet during the nonbreeding seaon (Hilty 2003, Schulenberg et al. 2010). Calls include "thin, high tzeer and peeping notes (Lane, in Schulenberg et al. 2010). The vagrant bird in Panama, likely a first year bird, called once as it flew, with a faint and brief, dry, fading trill (Robb 2009 et al.).