The 'bilabial trill' is a type of consonantal sound, used in some spoken languages.

He was actually referring to a voiced bilabial trill, often used as part of his vocal warm up.

This sound "bŕ" occurs very rarely for a bilabial trill.

Uripiv is one of the few well-documented languages that use the rare bilabial trill.

One unique feature of it is that it has both a voiced and a voiceless bilabial trill.

The bilabial trill is uncommon.

Features of the bilabial trill:

Similarly, a labiodental trill would be written (bilabial trill and the dental sign), and labiodental stops rather than with the 'ad hoc' symbols sometimes found in the literature.

There is a bilabial trill in two Brazilian languages, Oro Win and Wari' (phonetics.ucla.edu/appendix/languages/orowin/orowin.html) and what Dr. Ladefoged called "hissing-hushing fricatives" of Ubykh, once spoken in Turkey (phonetics.ucla.edu/appendix/languages/ubykh/ubykh.html).